What's the difference between these processor specs?

I'm buying a new laptop really soon (16" Studio XPS from Dell) and I'm a little torn on which processor to go with. The first is the Intel Core 2 Duo P8700 (3MB cache/2.53GHz/1066MHz FSB). The other is the Intel Core 2 Duo T9550 (6MB cache/2.66GHz/1066MHz FSB). The second is obviously better, and costs an extra $125, so I was wondering if it was worth it. My friend said the lesser processor would actually be better because it would prolong my battery life and cause less overheating. I'm tilted more towards a better processor though. Is the difference between these that big (in performance and battery/heat) or is it negligible wnough where $125 just isn't worth it? Thanks for any advice!