I would go with the 15" because of the core 2 duo, the better battery and the newer gen... and that 17" is the first gen 17", so there is bound to be problems...
OH, and Welcome to the Forums!!
Thx for the welcome, I have only had a mac for about 2 months, so I still don't know what I'm doing for the most part. As for the use, I boot to mac at work and run work apps (msoffice, term, xterm, etc...) At home I boot to windows to browse internet and play games (mostly FPS's). The 17" would be great for playing games and browsing the net at home. At work, doesn't matter much since i have a 20" external lcd. I'll probably get a chance to play w/the 17" since my 15" power button broke and sunk down into the laptop. It still works, it's just a matter of time until the button slides into it too deep and stops working. They are sending it in to get it fixed, but i have no other desktop, so they're giving the 17 to me as a loaner and possibly keep if i like it.
Back to the being a mac noobie, I love the design of the hardware, but I've still had OSX lock up on me which seems odd since that's opposite of what MAC is all about. Does it have to do with the intel architecture being new to mac? I just imagined it being much more stable. There are a lot of things i like about booting to the mac side, but windows is so familiar to me its just easier sometimes. And windows is so much easier to browse for and manipulate files and browse network shares. Just my 2 cents.