http://en.wikipedia.org/wiki/List_of_iPhone_OS_devices#Features
Regarde ici pour les différences...
Objective-C
Il y a bien une différence puissance :
http://en.wikipedia.org/wiki/List_of_iPhone_OS_devices#iPod_Touch
1st Gen :
620 MHz (underclocked to 412 MHz, originally 400 MHz) Samsung 32-bit RISC ARM 1176JZ(F)-S v1.0[20]
2nd Gen :
620 MHz (underclocked to 532 MHz) Samsung ARM11 core with internal ARM7 core for Jazelle acceleration[20]