Hello, I want to buy my first iMac and I don't know which one should I choose... Obviously, 27 have bigger screen, but in term of performance which one will be better?: 21,5" 4K, i5 3,4 GHz, 8 GB ram, 1TB Fusion Drive, Radeon 560 or 27" 5K, i5 3,4 GHz, 8 GB ram, 1 TB Fusion Drive, Radeon 570 Specification is very similar, but 21,5 have lower resolution, so maybe it's faster? Sometimes I play Starcraft 2, will 21,5" iMac handle with this game in medium/high settings? There was a time, when 27" iMac had a problem with dust inside its screen. Is this still and issue? Is it worth to buy bigger iMac just for better GPU?