If you are on the go a LOT, then the 15" may make sense for you. The 17" is significantly heavier (in my opinion), but I don't transport mine enough to make me not want the larger screen.
When I made my decision I finally decided that I would rather regret buying more than less
Simple as that.
I don't
expect to move the system more than once or twice a week in the coming year - and I live near school, to where the system would most often be moved. I'm not a heavy traveler, so I'm not terribly concerned with space on planes and trains, but I'd like to be able to use it wherever possible.
Really, I'm honestly not sure that I could sacrifice my beloved screen space for reasons of portability, but am also having trouble coming to terms with the prospect of porting around a bulky, 7 pound box. The 15" seems far more reasonable in that regard, but from my in-store tests, I doubt I'd be able to do a lot of simultaneous multi-window work without an awful lot of horizontal scrolling at any given time. Not fun.
I definitely did feel the weight you mentioned when I was lifting them up in the store, though; it's just 1.4 pounds different, but it sure feels like a decent bit more than that. I'm not a weak guy, but toss in a few textbooks and binders, and the weight adds up.
My practical side is saying "Get the 15," but my functional, screen space needing side is saying the opposite. I want to reconcile them, but they don't get along. Perhaps some alcohol would help smooth things out, but then they'd both just start crying over having to spend this much money in the first place.
If you want the feel of two screens you can adapt your workflow with Spaces; of course you won't have the real separate desktops like in Linux, but it will do well for you.
Most of my friends with MBPs do just fine with a 15" models; I would have gotten the 15" myself had I not been dazzled with the extreme niceness of the 17".
The problem is that in my field, screen space can be really, really important. Large musical scores and big, complex synth patches make for a tight fit on a standard 15" screen, particularly in the latter during live performances when I don't have a lot of time to scroll around to find stuff. I'm just torn between my personal needs for both portability and, er, visibility. It's a vicious circle - and the longer I think about, the more viciouser it gets.
I use both on a daily basis. One is the company-owned work 17", and the other is my personal 15".
For work, the 17" is great. I love the extra real estate, even though I also hook it up to an external monitor at my desk. For home, the 15" is better, as it sits around the living room and is easier to pick up and use for casual web browsing, email and the like.
This is unfair; no one should have this much power. And unless you brought enough for the whole class, you shouldn't have talked about it at all.
I'm telling teacher - you'll see, I totally will.
