What to get?

I can't comment on the photoshop part, but for university I'd go for a MBA plus external so you have the option of taking it with you to the library/class etc. You probably can't do that with the iMac lol.

 

Sure you can



As for the question at hand, I would go with the iMac and iPad combination.

Any reason you can't take the iMac to where ever you will be living?

That way you can use it for what you need and the portability role is filled by the iPad.

 

You could always get the MBA and an external monitor, mouse and maybe keyboard. Not bad for graphic art, and portable for school.

 

I can tell you from personal experience you will regret having only an iPad for mobile use while at college.

Sure, you can get by, but to be honest, having a complete computing experience on the go is a necessity. Whether in class (or lab), or in a library, or at group or friend's place, an iPad just won't cut it.

Sure, you can type an essay on an iPad, but you know how inconvenient it'd be if your reference material was also in digital form (pdf, on the web, etc.) and having to constantly switch back and forth? At least with an MBA, you can have them side-by-side.

I sold my iPad 2 and put the money toward an 11in MBA. I can do everything I could do on my iPad, and more. Anything I work on with my iMac, I can easily pull up and continue working on on my MBA. But my major dictates this necessity in a way, so maybe yours will be different.

I'd definitely suggest a 13in MBA, external monitor, wireless keyboard, and wireless mouse.

 

Why not spring for a 13" or 15" MacBook Pro and an external monitor and have the best of both worlds: a powerful, mobile computer with an external screen. The Pro has more processing power than the Air does, and then the iMac in question wouldn't be needed.