Just natives:
3.75s

function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call StoreInteger(udg_cache,"10020003","a",GetStoredInteger(udg_cache,"10020003","a"))
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction


---------
Just function call: 5.28s

function JustStore takes string a, string b, integer v returns nothing
    call StoreInteger(udg_cache,a,b,v)
endfunction


function JustGet takes string a, string b returns integer
    return GetStoredInteger(udg_cache,a,b)
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore("10020003","a",JustGet("10020003","a"))
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction


------------
+ I2S()    6.56s
function JustStore takes integer a, string b, integer v returns nothing
    call StoreInteger(udg_cache,I2S(a),b,v)
endfunction


function JustGet takes integer a, string b returns integer
    return GetStoredInteger(udg_cache,I2S(a),b)
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore(10020003,"a",JustGet(10020003,"a"))
       set i=i-1
   endloop


endfunction

---------------

+ H2I()  7.34 s


function H2I takes handle h returns integer
    return h
    return 0
endfunction

function JustStore takes handle a, string b, integer v returns nothing
    call StoreInteger(udg_cache,I2S(H2I(a)),b,v)
endfunction


function JustGet takes handle a, string b returns integer
    return GetStoredInteger(udg_cache,I2S(H2I(a)),b)
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore(gg_trg_err,"a",JustGet(gg_trg_err,"a"))
       set i=i-1
   endloop


endfunction

-----------------
+ Autoflush : 6.50 s (seems like Flush  faster than Store)

function H2I takes handle h returns integer
    return h
    return 0
endfunction

function JustStore takes handle a, string b, integer v returns nothing
 if (v==0) then
    call FlushStoredInteger(udg_cache,I2S(H2I(a)),b)
 else
    call StoreInteger(udg_cache,I2S(H2I(a)),b,v)
 endif
endfunction


function JustGet takes handle a, string b returns integer
    return GetStoredInteger(udg_cache,I2S(H2I(a)),b)
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore(gg_trg_err,"a",JustGet(gg_trg_err,"a"))
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction

-------------------------------
+ Autoflush / make sure it is not 0 : 7.59 s

function H2I takes handle h returns integer
    return h
    return 0
endfunction

function JustStore takes handle a, string b, integer v returns nothing
 if (v==0) then
    call FlushStoredInteger(udg_cache,I2S(H2I(a)),b)
 else
    call StoreInteger(udg_cache,I2S(H2I(a)),b,v)
 endif
endfunction


function JustGet takes handle a, string b returns integer
    return GetStoredInteger(udg_cache,I2S(H2I(a)),b)
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore(gg_trg_err,"a",JustGet(gg_trg_err,"a"))
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500

   call JustStore(gg_trg_err,"a",65)
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction


-------------------------------------
- Store unit now 8.09s



function H2I takes handle h returns integer
    return h
    return 0
endfunction

function I2U takes integer i returns unit
    return i
    return null
endfunction

function JustStore takes handle a, string b, integer v returns nothing
 if (v==0) then
    call FlushStoredInteger(udg_cache,I2S(H2I(a)),b)
 else
    call StoreInteger(udg_cache,I2S(H2I(a)),b,v)
 endif
endfunction


function JustGet takes handle a, string b returns integer
    return GetStoredInteger(udg_cache,I2S(H2I(a)),b)
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore(gg_trg_err,"a",H2I( I2U( JustGet(gg_trg_err,"a")) ) )
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500
   call JustStore(gg_trg_err,"a",H2I(gg_unit_Hmkg_0000))
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction


--------------------------------------------------------
Store unit with wrappers  7.62 **


function H2I takes handle h returns integer
    return h
    return 0
endfunction

function I2U takes integer i returns unit
    return i
    return null
endfunction

function JustStore takes handle a, string b, unit v returns nothing
 if (v==null) then
    call FlushStoredInteger(udg_cache,I2S(H2I(a)),b)
 else
    call StoreInteger(udg_cache,I2S(H2I(a)),b,H2I(v))
 endif
endfunction


function JustGet takes handle a, string b returns unit
    return GetStoredInteger(udg_cache,I2S(H2I(a)),b)
    return null
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore(gg_trg_err,"a",  JustGet(gg_trg_err,"a")  )
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500
   call JustStore(gg_trg_err,"a", gg_unit_Hmkg_0000 )
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction

--------------------------
Use a function call and auto return bug but just natives: 5.56 s

function H2I takes handle h returns integer
    return h
    return 0
endfunction

function I2U takes integer i returns unit
    return i
    return null
endfunction

function JustStore takes string a, string b, unit v returns nothing
    call StoreInteger(udg_cache,a,b,H2I(v))
endfunction


function JustGet takes string a, string b returns unit
    return GetStoredInteger(udg_cache,a,b)
    return null
endfunction


function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustStore("100003","a",  JustGet("100003","a")  )
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500
   call JustStore("100003","a", gg_unit_Hmkg_0000 )
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction

//===========================================================================
function InitTrig_err takes nothing returns nothing
    set udg_cache=InitGameCache("cscache")
    set gg_trg_err = CreateTrigger(  )
    call TriggerRegisterPlayerEventEndCinematic( gg_trg_err, Player(0) )
    call TriggerAddAction( gg_trg_err, function A )
endfunction

----------------------------
natives + return bug completelly directly: 4.53 s

function H2I takes handle h returns integer
    return h
    return 0
endfunction

function I2U takes integer i returns unit
    return i
    return null
endfunction

function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call StoreInteger(udg_cache,"100003","a", H2I( I2U(  GetStoredInteger(udg_cache,"100003","a" )   ) ) )
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500
   call StoreInteger(udg_cache,"100003","a", H2I( gg_unit_Hmkg_0000 ) ) 
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction

---------------------------------
just read directly 3.03 s

function H2I takes handle h returns integer
    return h
    return 0
endfunction

function I2U takes integer i returns unit
    return i
    return null
endfunction

function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call I2U(  GetStoredInteger(udg_cache,"100003","a" )   )
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500
   call StoreInteger(udg_cache,"100003","a", H2I( gg_unit_Hmkg_0000 ) ) 
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction

//===========================================================================
function InitTrig_err takes nothing returns nothing
    set udg_cache=InitGameCache("cscache")
    set gg_trg_err = CreateTrigger(  )
    call TriggerRegisterPlayerEventEndCinematic( gg_trg_err, Player(0) )
    call TriggerAddAction( gg_trg_err, function A )
endfunction

-----------------------------
Just read, but use wrapper function with auto return bug 2.78 s **

function H2I takes handle h returns integer
    return h
    return 0
endfunction

function I2U takes integer i returns unit
    return i
    return null
endfunction


function JustRead takes string a , string b returns unit
    return GetStoredInteger(udg_cache,a,b)
    return null
endfunction

function B takes nothing returns nothing
 local integer i=500

   loop
       exitwhen (i==0)
       call JustRead("100003","a" )
       set i=i-1
   endloop


endfunction

function A takes nothing returns nothing
 local integer i=500
   call StoreInteger(udg_cache,"100003","a", H2I( gg_unit_Hmkg_0000 ) ) 
   loop
       exitwhen (i==0)
       call ExecuteFunc("B")
       set i=i-1
   endloop

 call BJDebugMsg("!")
endfunction

//===========================================================================
function InitTrig_err takes nothing returns nothing
    set udg_cache=InitGameCache("cscache")
    set gg_trg_err = CreateTrigger(  )
    call TriggerRegisterPlayerEventEndCinematic( gg_trg_err, Player(0) )
    call TriggerAddAction( gg_trg_err, function A )
endfunction


---------------------

** Probably measurement error, it kind of means that it is as fast and not faster than the alternative that seems faster and turns out it didn't.