I've just run this code and I found that textmerge to file is 40 times faster than string concatenation using memory variable. It is true or I miss something?

#define _loops 20000
CLEAR 
? _loops, 'loops'
_t=SECONDS()
xx=''
FOR i=1 to _loops
	xx=xx+'123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890'
NEXT
?'String concatenation:',SECONDS()-_t

_t=SECONDS()
SET TEXTMERGE TO memvar xx NOSHOW
FOR i=1 to _loops
	\\123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
NEXT
SET TEXTMERGE TO
?'Textmerge to memvar:',SECONDS()-_t


_t=SECONDS()
SET TEXTMERGE TO xx.txt NOSHOW
FOR i=1 to _loops
	\\123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
NEXT
SET TEXTMERGE TO
xx=FILETOSTR('xx.txt')
?'Textmerge to file + FILETOSTR()',SECONDS()-_t
ERASE xx.txt