Should I sell my iMac and iPad for a retina MacBook Pro?

Hi all,

For a while now, I have been thinking about selling my late 2009 21.5" iMac and iPad 4 64GB in order to fund a new 15" retina MacBook Pro, but can't decide which is the better option.

I like having the iMac for 'proper' work and the easy portability of the iPad, but I also like the thought of consolidating them into 1 device. Plus, 99% of the time the iPad is just a £500 internet browser for me, which often makes me question its worth.

I'm into photography (also a potential career path) so I'd be using Aperture and Lightroom on the iMac or the rMBP.

In terms of costs, I can get £1000 for the iMac and iPad combined, and the 15" rMBP starts at £1500ish with education discount.

Half of me is saying keep the current combo as it works well and there is nothing wrong with it, but the other half of me is lusting after the amazing display, design and performance of the rMBP.

So, what would you choose and why?!