Neh if I had to choose an engine it would be the Luminous Engine, the best around now. It is developed by Square Enix for final fantasy XV. The engine is based on both the Unreal or Unity engine and CryEngine.
And I must say, it looks awesome.
There is more, why ppl choosing this or those engine. The grafical look is one, but todays engine looks all near same good, if they are using DX12.
It is more asked, how easy it is to learn a engine, and what tools the engine is offer.
An example: cry engine model inport allow only Maya or 3Dmax into the pipeline. With unreal you can inport every FBX model, so you also can use Blender for this.
2. Example: How easy is it to code the game? In Cry engine you can use Lua,C++, C script. Into Unrealyou can use a visual script engine and C++.
3. Example: how is the licence and cost to use the engine?
4. Example, how helpfully is support, documentation and tutorials?
5. Is there a large market place for selling and buy content?
7. Is there ahelpfully forum comunity?
There are a lot points, to think about,before choosing an engine and all is depending what kind of game you want develope. How are the cost to use the engine, if you sell a game, or just by using the engine. How easy it is to importcontent like models, textures, Materials.
How easy it is to generate the game project on different platforms, and there is a lot more to think about.
So every AAA engine is good or bad, all depending at you, and what you want make with it.
Change a engine, while a project is more or less done, is a really bad choice!!! It end up with a lot of work and frustration and a lot things are to do from scratch again.