Trying to help a friend decide between cMBP and iMac

Owns his own business(but just starting out) and has a YouTube channel. His old 2006 MBP is dying and he needs a replacement. He makes iMovie videos all the time(5-15 minutes long) and goes out into the field to give lectures.

I think the best combo for him would be an MBA and a 27" iMac to do his videos on. I honestly don't know whether to advise him on an i5 or an i7 and what configuration. The second thing is whether he should wait to buy the iMac now or will it be substantially updated in the next couple of months. I don't like the 21" because the RAM can't be updated and Apple's price for it pushes me to the 27".

He is toying with the idea of just buying a non-retina MBP. He's been running everything on a MBP up until now, but I don't know the demands of iMovie making. I would think he would need to wait for a new machine to
be out??

Has anybody got some educated opinions about what might suit his needs the best? Does he need to go with the i7 or will the i5 do the job with plenty of power to spare?

 

He's using the 2006 because that's all he had. It's been undersized for his needs for some time now.

My reasoning on getting the MBA now because it was all new and he could get it before the current machine died. That would give him the leeway to wait until the iMac was upgraded in a couple of months, although I'm not sure how many upgrades the iMac will be getting. The lower 27" iMac costs the same as the better 21.5" because of the need to have Apple install their expensive RAM.

It just seems silly to buy the cMBP now when it will be upgraded in the next couple of months. Even MacRumors buying guide has a do not buy recommendation on it.

Not trying to be argumentative, just telling you my reasoning.