I used Unity for a while as a hobbyist, and now unreal for several months. Just my $0.02:
Features - Unreal wins here, no contest in my mind. The material editor is great, as are blueprints. These are features you have to purchase on the asset store with Unity. I love Unreal’s overall more complete approach to an engine.
Documentation - Sorry, Unreal’s overall documentation has a long way to go. I generally find much better information on YouTube. I’ve seen several cases where it appears to be just generated, without examples, etc. Not all of it, but too much. Unity is far more useful in this regard.
Forums - Unity’s forums are definitely more active than Unreal’s. Sure, probably something to do with Unity has been around longer, but doesn’t change the fact. Anyone familiar with Unity and their forums will notice a difference in traffic pretty quick.
Programming - We’re getting into religion here. Let me just say…there’s a lot of snobs here. When I saw the documentation in Unreal for Unity developers, showing the C# you would use in Unity compared to the C++ you would use in unreal…holy crap, guys. Might want to take that down. C# is a much more elegant and clear language to work with, easily worth the -VERY- slight performance difference. But, I know it’s just a waste of breath. Which is sad, somebody at MS actually made the effort to support it in Unreal. Probably got threats or their house burnt down.
Support/Development - This is where Unity made it easy for me to leave. They seem to STRUGGLE with their engine, to add new features and improvements. The terrain system is an absolute joke, pretty much a no-go unless you buy something off of the asset store or make your own. They are JUST now getting a visual material editor, and from the screenshot I saw…it’s sorta gross. Also, when they do add new features they tend to be half baked. I just get the impression their code base is probably an absolute mess.
To me, Unreal seems to be moving forward much faster, with very nice features. They seem to be aiming high.
Bugs - I’ve had some pretty horrific bugs in Unreal. Datatable bugs. I lost a good bit of work due to Unreal forgetting the type of several critical objects used in the blueprints. It is a lot younger though, so it’s sorta to be expected. And, I see the Unreal team working hard to address them.
Overall, I feel like Unreal has much more of a bright future, due to the feature set and the professional presentation. If Unreal supported C#, Unity would die a very quick death, but since THAT’S probably never going to happen, we’ll have threads like these for quite a while.