I just went through this evaluation myself (weighing the 17-inch against the 15-inch), so I'll just convey what I've learned. There are 4 major differences between the two models, and you'll need to decide which features better fit your computing needs--and whether you're willing to pay more for them if required. Here they are, followed by my personal opinion about each one in italics:
*1) The screen.*
Three things to note here. Firstly, the screen is not only physically bigger, but has a higher resolution (the 17-inch screen contains 78% more pixels than the 15-inch). The upside is that the 1920x1200 display offers more room to work with (i.e. you can fit more windows on the desktop). The downside is that everything is smaller (some even complain that the fonts are a bit fuzzy), which may lead to an eye strain issue for some people over time. Secondly, the 17-inch screen has a 60% greater color gamut than the 15-inch, a potentially valuable feature to those who are particularly concerned with color depth and accuracy. Lastly, only the 17-inch MBP offers the matte screen, so for somebody who can't deal with the glossy display (as you may know, there are no shortage of complaints about the reflections), this may be the only option. I would recommend you visit the Apple store if possible to check these displays out in person.
+I was able to visit the Apple Store to check out all the models several times before I purchased. Let me first state that the display was not a deciding factor for me, as I personally liked both. I agree with those who say the 15-inch is easier to read (because of the lower res), but I also saw value in having more onscreen real estate to work with. The color gamut difference was not important to me whatsoever (and I couldn't tell the difference in person). Regarding the glossy versus matte screen, I also liked both but acknowledge that they are different. The glossy looks a bit "crisper", but I would give the edge to the matte screen (although I ended up purchasing a glossy). The reflections were not a problem for me. Also, in my opinion the grey bezel on the matte screen model detracts from the overall aesthetics of the body.+
*2) The battery.*
Two things here. The 17-inch battery lasts significantly longer than the 15-inch battery. At energy-saving settings this time can approach 7-8 hours, which is amazing for a 17-inch notebook computer. The other thing is that the 17-inch battery is not user replaceable--it must be replaced by Apple and they charge for it. However, the battery is supposed to last for 1000 recharges, so we're talking 3+ years of battery life.
+I'm never in a situation where I would be unable to use a power adapter so the battery wasn't an issue for me. If the power adapter was big and bulky like a PC adapter, I would probably value battery life more; but Apple's adapters are light and compact. This didn't factor into my decision.+
*3) The size.*
The 17-inch is longer, wider, and heavier than the 15-inch. This not only impacts portability, but also ergonomics since the way your hands rest on the keyboard is a bit different. Again, it's best to pick these up in person and get a feel for carrying them and using them.
+This was, along with price, the biggest factor for me. I typically transport my computer between several locations every day and use it in areas where there isn't much space. I also felt the 15-inch was more comfortable to use and manipulate.+
*4) The RAM.*
The 17-inch is expandable to 8 GB, while the 15-inch is only officially expandable to 4 GB. However, I've seen many unofficial claims of the latter being expandable to 6 GB. If you're into video editing or music production deep enough to require maximum RAM, this may be something you want to look into.
+4 GB is plenty of RAM for my needs, so I didn't investigate this further.+
I made my decision last night and purchased the MBP in my sig over the phone. I felt the bump to 2.93 GHz wasn't worth the extra $300. I did bump up the HDD though. I should have it in about 2 weeks, at which point I hope to post a review indicating that my new MBP is defect free and in perfect functioning condition. Stay tuned!
