Yes and yes. Photoshop unless you are getting into like 30 layers runs very fine on both. And if you are using Finac Cut both can handle 4K just fine (again,unless you are into professional video production)
If you're talking about once in a while, no problem. The main advantage of the 15 inch comes in cases where you need to process a lot of them all the time, in which case the speed up will become cumulatively significant.