I agree with thegoldenmackid; no one can predict what will work for you. On the other hand you're asking for opinions so here's mine:
I've owned two 15" MBPs and two 13" MBs, including last year's unibody MB.
If you work on the go and you want a machine you can take and use comfortably anywhere, those two inches between the 13" and the 15" make some difference. I lugged my old 15", literally, right around the world. Although it didn't kill me, it was a pain in the *ss; 15" machines don't easily fit into all bags; they don't easily fit on an airline table; they don't easily fit on the small desk areas in the back of OB trucks etc.
Functionally it was brilliant. Portability-wise it was sort of ok.
When that machine died last year I had to buy something quickly so I bought the 13" MB because I really wanted a small machine and thought I could work around the lack of firewire or that Apple had some kind of technological bridging idea in mind. I couldn't/they didn't. It turned out to be an expensive mistake, although the size was perfect.
I've just upgraded to the 13" MBP and for me, as a pro writer/producer/director it really does represent the best of all worlds; the size, weight and functionality balance out. The screen is absolutely fine (would be better matte, but that's another issue). It seems to run cooler than either the 13" or 15".
Right now I couldn't be happier.