As I have stated many times Semprons "PR" is compared to "CELERON" and the XP's "PR" is to "P4".
That is why a Sempron with a higher "PR" is slower than a XP with a "PR" that is lower. Its very simple.
The Sempron's are all either Thoroughbred "B" or Thorton, which is the Barton core. I had a Sempron 2200+ (1.5ghz) and that thing would OC like crazy. I got the FSB up to 235mhz until my memory wouldn't go any further. And that was on STOCK Voltage. So, about 2.2ghz on stock voltage. Not to shabby 🙂
But if you are not going to OC, then get the XP since it has a higher mhz. So, it will be alittle bit faster than the lower clocked Sempron.
Jason