What are the disadvantages—if any—to getting a 4K external display to use with a new 2015 15-inch MacBook Pro? In particular, I'm wondering if running a 4K display would hurt the Mac's ability to do (FCPX) video and photo work. I.e., would the Mac be overworked all the time? For reference, I'm talking about the high-end MacBook Pro with dedicated GPU, and am comparing the Dell UltraSharp P2715Q (4K) to the U2715H. I can't see either in person, so have no idea what the U2715H looks like in comparison to my U2412M. Maybe it's so much better I don't need 4K!