Does the extra 2" makes a huge weight difference?
How about in terms of performance?
I don't do any editing, just a little gaming.
I have a macbook and a new uMBP 15" top of line(with a little extra, 3.06) it is not significantly heavier, nor bigger than the 13", for me that is, the 13 is smaller and more portable, but for me(i am tall, and have big hands) the 15" is perfect, in terms of performance, it blows any of the 13" uMBP's out of the water, look at benchmarks at various review sites, the 2.8 w/512 9600gt is an incredibly powerful machine, using it with FCP 6, it is faster than my DP g5, and handles beautifully, in terms of usage, it is overkill unless you use it professionally(FCP, Photoshop, extreme gaming, etc) so it may be better to stick with your machine, but here are a couple of big differences to me
1) the screen is better, yeah they improved the 13" screen, but Apple still keeps some advantages to the 15" and 17" despite what they may advertise. The Colors are amazing, and they pop of the screen, having seen both the 13" and the 15" in person, and having the new 15" i can say that it is much more beautiful
2) I love having the choice of 9400m/9600gt, because i do not always use or need the full potential of my machine, but when using FCP it is not too difficult to switch
3)bigger touchpad
4)Run's cool, i have never had a burnt hand or had the machine break 56c yet, under intense usage
5) the speakers are louder and sound better
6) the screen is bigger
7) it looks cooler, i mean, there is just something about the 15" that screams beauty, and the 13" lacks it
but it comes down to you, it sounds like you do not need it, but you want it, so if you can justify it, go for it, but if not, be happy, or make the choice that is best for you, and do not base your choice on others opinions, even mine, I was just stating what i love about the 15" and why i would not have bought the new 13"