I’m just going to be a (small) voice from the other side I like working on a Mac and UE4 has gotten significantly better with every version to the point where its pretty much always 60-100+ fps on my 2012 iMac now. (I know this would not be the case on the 5K). I want UE4 to stay on the Mac and the more I use it and feedback I can be part of that. I also have high(ish) hopes for the Metal version which is currently set for 4.11 I believe.
As for super high res - I believe UE4 editor is not good for really high res screens on any platform yet as there are some things that need fixing in slate. Unity still does not have retina support even though they have been trying on and off to get it working all year. Its just not something that happens quickly unfortunately.
Anyway summary is it is getting better and working in a Mac has gone from pretty much don’t do it to pretty comfortable IMO.