Unity delivered poor rendering several versions ago, now it doesn’t, even out of the box, it’s become pretty sophisticated even with no Asset Store. But of course, they rely a lot on the Store, it’s their business model and it’s not necessarily bad.
I’ve been using Unreal consistently for a couple of months now, and I’m very satisfied (just a little annoyed with some loading times, saving times etc and rare crashes).
Saying UE4 or Unity is older I believe may lead to very controversy conclusions; First of, older may mean many things, good and bad. It may mean to be more consistent, more stable, or may be slower, outdated. I tend to believe that the good code was kept kind of intact in UE4 and the outdated code was rewritten, but we can imagine some of it still exists and may slow UE4 down.
Unity was built to be fast and simple from day 1; on this I believe they have the edge. On my experience Unreal is slower in the editor itself.
As a designer, I believe Unreal is more designer friendly, though Unity is simpler to use overall. At the end of the day I don’t think we can say one is older than the other, that really depends. Unreal is surely more robust.