Newer CPU. The hardware is not identical, they use different CPU's in many models of BlackBerries even though they all use Java.
Basically, totally different brands CPU's can exist in all the Java BlackBerries, and Java is used to make them identical.
It just so happens that the new Qualcomm CDMA2000 1X-EVDO chip also has an integrated 250 Mhz ARM9 CPU, which runs much faster than the other CPU's currently used for GSM/GPRS.
However, wait till the new EDGE BlackBerries come out. (Don't know when though, but everyone agrees it is going to be happening