I use a 15" with less impressive stats (RAM, Hard Drive) and it works fine for me. I use a tricked out Mac Pro at work, and of course, it's better, but my MBP works great. If I couldn't have both a desktop and a laptop, I'd go with the MBP for sure. I would stick to a 15" if I were you, though. The 17" is HUGE and kind of takes away from the mobility standpoint. The only reason I would say get the 17" is if you really want to use Color.
At the 11th hour (yesterday) I went with a 24" iMac. Just couldn't pass up the large screen for actually a little less than the laptop. Just set it up today and it is very powerful compared to my older G5 Pro Tower. I have a 12" macbook that'll have to do for any traveling I'll do.