Do you realize AMD is not ATI and the architecture of both hardware and software is changing, getting better to catch up with the competition?
If you're an Nvidia user, of course you have to rely on the information given by others, so all you can really do is speculate, but I'm not speculating here when I say that I've played many games on this AMD GPU with no issues whatsoever.
I was an Nvidia user before this AMD build and I can tell you that was a horror. Particularly with driver issues on the laptop. Every new driver they released fixed one thing, but broke something else. Another Nvidia GPU, this time in a desktop PC simply broke, because it got too hot and its fan wasn't able to cool it down enough, so the GPU had to be replaced because it was not useable anymore and the list goes on, I had my own negative experience with Nvidia and always admired what AMD users can do in their driver settings that were honestly always much easier to understand and navigate through, even for new users.
As for the documentation that's supposedly somewhere out there to prove that AMD is a worse option, here's some other sort of documentation which doesn't make Nvidia look so good at all either -
here and
here...
Funny, your argument was the compatibility with Unreal Engine 4 and yet my own experience with it was pretty satisfying on this AMD GPU. Why should OP pay more to achieve the same results? Especially if he's interested particularly in this one game which runs on Unity engine and not Unreal Engine 4 which in itself is a whole different story?
But ultimately, it's up to him to decide which GPU to buy...