MacBook Pro retina 13" vs iMac 21.5" 2011

When thinking of buying a Mac, I always wanted to have one for my desktop. So I always consider an iMac, but my last birthday present was a MacBook Pro 13" retina. I'm very pleased with it, I enjoy the retina display, the USB 3.0 for my external drive, HDMI in my TV, and the trackpad. But last week me and my girlfriend broke up and had a major fight, somehow in the middle of the battle the MacBook got damage. It is a bit bended in two corners and the display have a little crack, but doesn't affect the image in the screen. It's painful for me to look at it with those two details and someone offered me the option of trade it for an 21.5" iMac 2011. I'm very confused, I know I would miss the MacBook retina features, but also pleased with the larger display, of the iMac.
I would like to hear some opinions, it will be very helpful. (Hope I made my self clear with this situation)

Your first decision is...do you need the portability of a laptop computer. An iMac is obviously not portable.

As far as the display size of the iMac. If you like a larger display...just purchase & use a larger external display with your MacBook Pro.

- Nick