A lot of bias opinions here. But mathematically, Unity is Cheaper than Unreal now. If your game is successful it will be stuck with a 5% royalty for its life, which will always be more expensive than the eventual 1500 to 3000 needed for Unity Pro. Period. If your game is not successful you will never reach Unitys 100k limit or Unreals 3k. (Though hitting Unreals is far more likely).
However competition is good for both engines as now they can be judged for their features instead of price as they were before.
Looking at the state of things today if I was making a next gen top graphics game I think Unreal is the clear choice. You can look at Unity’s videos and see that it can’t produce the same level of detail as Unreal.
However as far as mobile and platform support I think Unity is the clear choice here. Unreal has a ways to go to catch up in the mobile area and 2D field. And their are many platforms Unreal doesn’t support at all.