You could have answered your own question by writing a simple benchmark

Code:
Break ON
$iIterations=999999
$aLoops="For $$i=1 to $iIterations Next",
	"While $$i<$iIterations $$i=$$i+1 Loop",
	"Do $$i=$$i+1 until $$i=$iIterations"
 
For Each $sLoop in $aLoops
	"Benchmarking "+Split($sLoop)[0]+@CRLF
	$iStart=@TICKS
	$i=0
	$=Execute($sLoop)
	$iEnd=@TICKS
	"Start: "+$iStart+@CRLF
	"  End: "+$iEnd+@CRLF+@CRLF
	" Time: "+(CInt($iEnd)-CInt($iStart))+" ms"+@CRLF+@CRLF
Next
  
Exit 0