Years ago, I remember some conclusion that ...

if  %x > %y  { return $true } ; <-- is faster
if (%x > %y)   return $true   ; <-- is slower
if (%x > %y) { return $true } ; <-- slower still

This is another reason why it's necessary to code for style over performance. What performs well one year, may not the next. Though, if I were performing a very resource heavy task like scanning a harddrive, sure, I'd squeeze every last bracket for an extra ounce of speed. But then again I'd probably write such a program in C++ or at least AutoHotkey.