How important is GPU for iMovie?

Hi there,

I am thinking about buying a new retina MacBook Pro, however price is very much a factor for me. In an ideal situation I would just go ahead and buy the top specc 15", however perhaps I don't have to.

How important is GPU for iMovie editing? For example I currently have my eye on the high end 13" model, but if it can't edit 1080p video well, then it really isn't worth buying for me.

If you actually own a high end 13" retina macbook pro and edit 1080p video (MPEG) on it, I'd be very appreciative if you could let me know how it does.

Otherwise simply answering the question of GPU usage for iMovie would be great!

Thanks in advance!!!