Need help deciding -13 MBP vs 15 MBP (2011)

So , for the past for years I have been using a 13in MB and now is around the time that Im going to upgrade to pro series , but can't seem to figure out if the upgrade to a 15in over a 13in is going to be worth it. I Tend to do alot of media work on 27in iMac that i share with my brother but since he opened up a studio to do work in i longer have access to the iMac on day to day basis.
While I know that the 15in is supposed to be better than the 13in MBP Is it really that much more powerful? Regardless of which one I buy Im going to be running minimum Cs5 Photoshop and Illustrator on it.
Only real reason im considering the 15in is because of the graphics card ( if i decide to play some games on it) and because its supposed to be more power. I have read benchmarks but there just numbers to me. I would like to know if any here actually considers the difference in models to be of great benefit or if its just greatly over-exaggerated. When I Do buy it later this year when lion comes out I would be purchasing either the high-end 13 or the high-end 15 so any advice is greatly appreciated.

It a pretty significant difference but unless you will be gaming or your illustrator gets really intense you wont notice the difference. Also if you are at all considering the 13inch there is no reason you need the high end 15.

Well , thats the thing gaming is just a perk. Only reason I like the 13in is cause of its size. But if the 15in has significantly more power when it comes to running illustrator smoothly as well as other cs5 based programs then I would go with 15in, cause I plan on using this next computer for another 4ish years.

I guess what Im asking is on a scale from 1-10 how much powerful is the 13 v 15 MBP.

All the CS5/5.1 design standard elements ran fine on my 2008mbp to be honest. The 2011 just runs them better. If that makes any sense.

if i were to choose between the 13in models... i'd go with the baseline model. there's little improvements in comes to speed and power compared to the 13in i7 model plus there's some issues with the high end 13in with regards to turbo boost especially when running bootcamp on it.

if i were to choose between the 15in models... i'd go with the high end model. the 1GB dedicated GPU is a big difference with the 256MB dedicated GPU the low end model has to offer.

so if money is not an issue i'd go with the top of the line 15in model.