khahesh mikonam aziz
glad to see Iranians here:)
Well 2.5GHZ CPU with 6MB cache perform better than 2.4GHZ with 3MB cache especially in cpu intensive apps
well if u go with OS X leopard u will have less erros and bugs but u are limited with programs,most apps are for windows.also i dont recommend u getting MACBOOK because its not built to do heavy tasks,i say if u need OS X go for MACBOOK PRO and thats expensive IMO.
I would go for Windows because aside from the less bugs and errors that OS X has windows has more apps IMO.