From what I gather, a CPU can never be "guaranteed" to OC to any level. It simply depends on the quality of your core. However, the T'Birds and Durons are comprised of the same core, the only difference being the amount of onboard cache. If I remember correctly the 256K L2 cache of the T'Bird generally yields about a 15-20% increase in performance. Correct me if I'm wrong fellas, if so, I apologize for the mistake. From what most people say, and after seeing the results of what the Durons can pump out in terms of OC'ing speeds, and benchmarking results, and of course you want the best bang for your dollar, I'd say Duron. I personally bought the T'Bird, but I had a little extra money at the time, so that helped my decision. Hope that helps....
Rabie