I'm a Intel man myself (don't hate me because I'm faster
No problem, we won't 'cause ya ain't
Seriously, it depends on the applications, the core, and the system configuration.
The best Throughbred cores (Tbred) are the "B" versions. The most common of these are the 1700+ & the 1800+ (they're getting more scarce). Most of them will hit 2.4 - 2.5ghz.
The Thorton cores are Bartons w/ 1/2 the cache disabled & should O/C like most Bartons, minimum of 3200+. With Barton cores anything above 2.2 is good (most are getting in the 2.3 area). The Thorton might get a bit higher due to the reduced cache, but you'll need 100 - 200mhz extra to overcome the extra cache of the Barton.
It depends on the system config you're planning. For example, if you're have limited FSB speeds then you'll want either an unlocked core OR one with a locked higher multiplier.
For example, w/ an Nforce2-Ultra board & PC3200 RAM you can -
XP 2500+ (Barton) = 11x200 = 2.2ghz (very likely)
XP 2400+ (Thorton) = 12x200 = 2.4ghz (maybe)
XP 2200+ (Tbred) = 13.5x200 = 2.7ghz (not likely)
For example, w/ a "333" board you can -
XP 2500+ (Barton) = 11x166 = 1.8ghz (stock - lol)
XP 2400+ (Thorton) = 15x166 = 2.4ghz (might)
XP 2200+ (Tbred) = 13.5x166 = 2.2ghz (likely)
All AMD chips are multi locked starting on or around week 39 of this year so if you're going with a slower FSB board, that runs around 166 (333) then the higher multi will work to your advantage.
Check my sig, a MB/CPU/RAM combo that runs just over $200 - pretty damn cheap for the performance.
It breaks down -
XP2500+ = $86
AN35NU = $64
256 PC 3200 = $55
My choices would be -
1. 200fsb = XP2500+ ($86 - good bang for the buck)
2. Less than 200 look for a "B" stepping of an 1700+ or 1800+
Also check the links in this thread, lots of good info about the different cores.
http://www.ocforums.com/vb/vb/showthread.php?s=&threadid=250008