Which Mac configuration is right for my use?

My rMBP 15" is on its way to turning 5, and I have decided to upgrade while I can still get a decent sum for it. The prices on the new MacBook Pros were.. spicy, but I have the finances and I am considering buying one. Personally I thought the new TouchBar seemed like a great tool.

I do mostly amateur photo editing, college work and I have Logic Pro which I plan to learn. I used to use Aperture for photo editing, but after it was discontinued I've used the Photos app, as I still haven't brought myself to buy the Adobe Lightroom/Photoshop-package. I use roughly 200 GB on my rMBP. As I have an iPad Pro 9,7" with keyboard that I use on the go, portability isn't too important.

I will never buy a computer with less than 16 GB RAM. However, for the rest of the specs I'm not sure what I need. I'm considering:

* High end 13" MacBook Pro: 2,9 Ghz dueal core i5, 16 GB (upgraded), 512 GB SSD, Intel Iris Pro. $2199.
* Base 15" MacBook Pro: 2,6 Ghz quad-core i7, 16 GB, 256 GB. Radeon Pro 450 with 2 GB. $2399

So for 200$ I get a quad core i7 instead of a dual core i5, and dedicated Radeon 450 2 GB instead of Iris Pro. I also get a bigger screen. But considering what I do on my Mac, do I need that horsepower? Will I ever notice the difference in performance? How much more futureproof is the 15"?


Also, just a wild thought, would this iMac 4k be a better alternative?

* iMac 21,5" with 4K: 3,1 quad core i5, 16 GB 1867Mhz RAM, 512 GB RAM, Magic Trackpad: $2149.


What would you recommend for me? (I should buy as this year is my last chance for the student discount).