Well I've posted this a few times in here, but my story may help.
I started off by selling my old non unibody 15" 2.2 Core 2 Duo Macbook Pro, I then purchased a 13.3" Macbook Pro with the better battery and new screen.
The new screen was in fact nicer than the Macbook Pro I sold, however my old Macbook Pro was matte and the new one is glossy, so naturally it was more vibrant, but otherwise it wasn't a night and day difference by any stretch.
I then decided that the 13.3 was too small for me, I wanted my 15" screen back. So I returned the 13.3 new model with better battery, better screen etc etc for the previous 15" Unibody 2.4 which has the stand alone graphics card. I do like to game on occasion and edit videos so I wanted to have better video performance, that is not something to be ignored when buying a Macbook Pro. In fact I believe that the Macbook Pro is a Pro partially due to better video performance thanks to the discrete graphics card. The 9600m GT is no gaming powerhouse, but it is a very capable card and doesn't share system memory.
First of all, I notice NO difference between the two screens. I was worried about losing out on the 60% color gamut increase but I'm telling you, unless you are some photography nut and have the sickest eyes known to man, you will not notice the difference. Not to mention the 13.3 looked slightly washed out compared to the 15" I now have, it may be the color profiles on each, but I actually think the 15" looks better in richness than what I had on the 13.3.
Now on to battery life......the battery on the older unibody is very good. I had to charge my 13 and I have to charge my 15, battery time is dependent on what you are doing at any given moment and that is always going to change when you are on the machine, but quite frankly I feel no loss not having the newer battery. Battery times are always BS when stated by Apple or anyone else, I don't notice the difference. The battery time on the 15" I have now is way better than what I had on my older Macbook Pro, so I'll take that as an upgrade in itself.
I say get the old one, and I am speaking as someone who has had both. Please do not use the screen as something you may be losing out on, unless you are ALWAYS on the go and need every minute of battery power you can get, that really is a non issue as well.