Any recent dual core processor will blow any Celeron away. The Celeron processor, even when it came out, was never a great chip. It was released to be a budget processor. I have also heard from some computer techs that Celeron's don't run at their full clock speed.
But it is not just the clock speed of a processor that matters, a lot of it is the architecture of the chip. Taking Intel's Core2Duo line for example, it has quite a few platforms the most recent being Penryn, and before Penryn is was Santa Rosa. And if you were to compare a 2.5Ghz Santa Rosa chip to a 2.5Ghz Penryn chip, the Penryn would come out about 10% faster - because of its better architecture. And the Penryn wasn't truely even a new platform, it was a "refresh" of the Santa Rosa platform so other performance gaps would be larger.
Brandon