best advice i can give you is to choose your dream laptop/s and go to a store lift it for few minutes, you will know if you like carrying it around or not. I upgraded from a 15" to a 17". 17" is a heavy laptop and is usually bought as a desktop replacement. it is not meant for carrying around but i strongly recommend that size.

Got it thanks! I'll take that into consideration. I was also thinking that a 17" might be easier on my eyes in the long term.

go for 17".

know a few people with 17" and I have know idea how they lug that to and from class every day!  But if the jacked shoulder muscles, and larger screen are worth it for you and you can afford it I'd probably go for it.  Also take into account what the computer lab situation at your school is, some people use the large screens in the lab for intense detail work and their non 17" laptops for everything else

I own a 17" dell alien ware and it's rather massive. I'm a tiny girl and it's a chore hauling it to  school everyday, but I got a great price for it and and I'm more than satisfied with it's performance. I agree if you don't mind hauling it around and you can afford it, go for it. 

Okay thanks guys!

I have a Lenovo W520 15.6" and a USB Powered 14" screen from Lenovo, so i now I have dual screens.  14" portable's so light and it doesn't add much to overall weight.  Wouldn't you rather want dual screens, instead of little increments?  W520's about 6lbs and packs great power for its price and size.  I especially like 95% color gamut screen that displays great color range.

oh I have 2000m for W520.. it comes in handy for autocad (runs smoother) and some hardware accelerated apps - photoshop cs6, premiere pro cs6, 3ds max.  3ds max utilizes hardware renderings and Revit might not support 2000m or 3000m yet.  You might want to check all the apps that you are going to use and find out whether they support these graphics cards or not. I didn't see much performance boosts in Sketchup and Rhino though.