As far as feature parity, Mac has been playing catch up, though I’m not sure exactly where it is now. But for example you need to use 4.18+ for VR on Mac: https://www.roadtovr.com/unreal-engine-update-brings-native-support-arkit-arcore-steamvr-support-mac/
For performance, Epic’s stance on creating games with Unreal is a fairly beefy computer (including gpu which Mac generally drops the ball with) https://docs.unrealengine.com/en-US/GettingStarted/RecommendedSpecifications/index.html
“Copious amounts of RAM is the single biggest contributor to a smooth user experience. While the editor and engine don’t use 32 GByte, having the memory available for the disk cache is a boon, especially as a programmer compiling the full engine. We found going above 32 GByte resulting in diminishing returns.” https://wiki.unrealengine.com/Recommended_Hardware
“For developing with UE4, we recommend a desktop PC with Windows 7 64-bit or a Mac with Mac OS X 10.9.2 or later, 8 GB RAM and a quad-core Intel or AMD processor, and a DX11 compatible video card. UE4 will run on desktops and laptops below these recommendations, but performance may be limited.” https://www.unrealengine.com/en-US/faq
" Note: We get too many questions from people who do not even meet minimum requirements, wondering why something does not build or run. So please, just because you are running Linux, it does not mean you can use some 10+ year old clunker of a computer to build and run a next-gen game engine (which UE4 is)." https://wiki.unrealengine.com/Building_On_Linux#Prerequisites
As you can see they have the info all over the place for some odd reason 
but its there.
Of course when learning or smaller projects you don’t need a beefy computer. At some point it would make sense though. At the same time you don’t want to learn with it running poor either. A decent $600 gaming computer (Mac will cost more) will be fine for learning.
I’ve decided to use Windows so that I (hopefully) won’t have many problems.