Which overclocks best? Athlon XP T-bred or Thorton?

[masshass81]

lookin to get a cheap cpu and overclock it, lookin to spend at most $65 on the cpu. But I dunno which core overclocks better, T-Breds or Thortons?

Or how about OCing the Sempron, I havent found or read any info about it's ocing capabilities.