when it comes to cross-platform compatibility, there are not so many choices. unreal engine is expensive to license + needs lots of performance and optimization (see firaxis xcom).
unity is very well optimized for apple for example. as a mac user i very much appreciate the choice of unity, it also means, it can run on ios. i i like to have a game that runs well and looks good instead of looking fantastic and running unstable, choppy.
From a PC gaming/end user perspective, I had a lot of fun and very few issues with Broforce, Darkwood, Endless Legend/Space, Hearthstone, Kerbal SP, Shadowrun, Sunless Sea, Deserts of Kharak, Layers of Fear & a few more recent games, so I’m perfectly OK with PP being on the Unity engine.
I’m still playing Space Hulk & Battletech now and the only really bizarre issue I’ve had was installing the latest version of Citrix Workspace caused Battletech to crash with a Fatal Exception error instead of loading, which apparently was due to a conflict between Unity games and the Citrix Worspace app. No idea why or how, but dropping back to Receiver from Workspace fixed it. I’m pointing the finger at Citrix more than Unity, given how long the engine’s been around for compared to the new Workspace.
Real Computer Graphic engineer here. I am, as most of my co-workers are, very anti-Unity. First reason is horrible default shader it has, that you can spot from a mile away. Any light calculations are way longer that they should be, unless you polished it very hard for what you are doing, or made a new shader that does not suck. Make no mistake, it sucks, no arguments or doubts. Second is it can have some problems with some other programs, at least compared to Unreal you mentioned. And third, its actually slower to develop than in Unreal. Now, I’m not saying Unreal is always better, but it is in 70% of the time. HOWEVER, Snapshot games choose Unity for a reason. Maybe they are better/more experienced at it, maybe they got better deal for licence or maybe they have some specific implementations in mind that would not work in Unreal. Probably all three, if I had to guess. As for the 3rd reason of the 3rd reason, you must remember that game engines are not tool, they are skeletons and internal organs. The skin you put on is, well, a skin deep.
as a developper also, i am working on both engines and my favorite is unity.
Unreal is really good, but there is so many crashes for nothing…
i will not evaluate more than this point wich is capital if you want to avoid stress