Unreal Engine 4 is now available to everyone for free

>The engine is also open source

I think you mean the source code is available (i.e., anyone can download it), which is different from its coming with an open-source license, which is what most people mean by "open source".

Free until you take more than 3000 sips from the glass per quarter. So still likely 100% free for all but the successful indie devs and larger studios.

"Ideological purity" is irrelevant. The point here is that people are abusing terminology to create ambiguity. As we are talking about software, the term "free" has specific connotations that differ from everyday language.

UE4 is a source-available, gratis game engine. This is fine. It is not open source, nor is it free or libre.

It's hard to compare unity and unreal. To answer the question about c++, with UE4, the blueprint system removes almost all of that. Entire games can be written in their visual programming language. I also think there are ways to use c# (https://mono-ue.github.io/), if you prefer that as well. C++ is needed if you want to extend the native classes.

Regarding the editor, unreal is pretty amazing. It really shines in the tools department. Check out the landscape editor, materials editor, and animation tools on youtube. Pretty fantastic stuff.

The game engine itself is better than unity in almost every way with a few big exceptions:

1) multiplayer map size. unity can pretty easily support large online worlds 2) support for mobile/tablets. unity is the dominant platform on those devices. 3) community support. unity has a much larger community, better documentation, and a much more populous online store (though unreal is catching up)

Can you even compare them :)

Evaluation of software, be it library, framework, sdk or a whole engine+tools is much much harder than writing actual software, especially when royalties, copyright and other legal issues are involved.

In reality there is no way of knowing what would do your best, so you can look at specific bad parts and take that into decision making, for example, for what I've heard (and possibly it could be wrong):

- Unity is not really good when lots of people have to edit the same files, merging is not really good, and the server option does not really cut it. (For example Quake's engine .map text files are not so bad to merge in cvs/svn/p4/etc.)

- Unreal had always had the bad "fame" of 30-only fps game, while this is okay for certain shooters, or 3rd person games, it would've never worked for "Call of Duty" where the brand was simply established with 60fps. To some people this might sound a bit pedantic, but 60fps matters! (And >60fps does not really, unless you need to swap frames for a 3D VR device of sort)

That to be said both engines surely have really good parts. From little I've explored in Unity, what got me first was the ability to extend the editor while it's running - I could add menus with functionality while it was running - this is super cool.

Unreal on the other side is well known engine with lots of people from the AAA game industry familiar with it, and while the editor might seem completely foreign to people starting in the game industry, it's pretty well known by many others (I guess they don't advertise it much).

The hidden gem of Unreal for me, was it's internal UI system, which could be used as a separate project - it has docking, controls, etc. - it might be a good replacement for Qt, MFC, wxWidgets, etc.