Honestly I am only beginning to edit, but I have found myself on a budget so I bought a 13″ MacBook Pro, if you know your workflow and get the right equipment along with it you won’t see any setbacks. What I did was got the fastest 13″ MacBook Pro then got 3 HDD’s that I had running at 7200 rpm, then got my 24″ LED Cinema Display. I have not had any problems yet and when I’m on the go I can use my 13′ with ease.
Then again I’m not the next Motion Picture hit editor.
You just need to know what you will be working on and what footage you use.
Best Regards