i want something portable and good for use of after effects,photoshop,dreamweaver,flash etc... only thing letting me down for the 13" is the screen resolution, and maybe the 15" is too big to carry around?
I carry around the 15" just fine. If you think the 13" has insufficient resolution, you're going to have to get the 15" or 17" anyways. It's up to you what's more important.
I use 13" to carry around, it's just more convenient. If you get an external monitor that will do you for the higher res, more screen realestate which sometimes you need.