Frankly any comparison is going to be superficial unless the comparison is done by a person who has actually shipped a non-trivial game on both engines.
So many of the problems you run into making a game on Unity, Unreal, etc come down to the out-of-the-ordinary requirements of your game and the inevitable peculiarities of the engine itself. Part of becoming an "expert" in building games on a third party engine is knowing where the pain points lie, where you should absolutely not fight The Way It's Done, and what bugs remain unfixed for years on end (Unity asset bundle system, looking at you).
Edit: My point being that unless you know the needs of your particular game and have familiarity with a candidate engine, it will be very difficult to determine if your choice is "best" or not.
Reminds me of all the "Lets make a battlezone like shooter"-gamedevs who dropped by on the Spring-Engines dev site. And yes, you are perfectly capable to do that.
And no, it wont work well- for the reason, a RTS-Engin has a built in lower physical Simulationframe update- and is allowed to act "slower" to commands then a shooter. So, if you want that shooter to happen- engine rewrite it is.
They'll be competing similar to Shiva Engine, it will be a mindshare battle as they aren't the first Unity competitor.
Unity is the most known and jobs and markets have sprung up around it as well as a massive asset store now exists, it also has many integrations such as apis and tools that take years to acquire.
Unreal and Epic have Tencent money and are on the way.
The OSS side of this engine is pretty interesting. Will be fun to have another competitor in this area. Xenko looks like a direct Unity competitor even down the the pricing and tiers. The big challenge is the community, asset stores and launched titles under the engine. Branding is important as well, to me Shiva and Xenko are forgettable brands, Unity and Unreal are set in minds.
