Ho do you figure? My XP-M was easy to get to 2.53ghz... only took a week of hard Prime95 testing
I said 'especially the ram and getting it stable' meaning the RAM will go further, be more prone to staying stable. Socket A's your RAM won't go very far, 250MHz you'd be VERY lucky with 1gb of RAM to achieve not to mention you'd have to have aftermarket NB cooling and possibly a voltage mode to give that NB enough volts just to get the RAM stable up that high.
AMD64s as far as CPUs are concerned require the same kind of testing the socket A does.
But it really comes down to this....have you overclocked an AMD64? If not, then can you really argue based solely of things you've read or maybe a noobs mistake?
You know for a fact I've overclocked an XP-M and I can tell you my current machine is an AMD64 overclocked, CPU & RAM so I can tell you from experience the AMD64s have been rather smooth.