UE4 is great, I use it all the time. I doubt EA would ever license a competitor's engine, however.
In terms of graphics, frostbite is just as good, if not better, but there are plenty of horror stories from developers who struggled to make it do what they want. Basic things like inventory management, companion AI, and save/load functionality had to be added in for DA: Inquisition.
Unreal is so successful because of its business model, which puts it in the hands of anyone who wants it. There's a massive amount of collective knowledge about it, and really solid official documentation. Frostbite lacks all of that.