I came from Unity to UE4, and imho the grass is not greener on the other side.
Also, I don’t believe it’s fair comparing UE4 and Unity on the documentation level. Fact is, UE4 is a very young engine as it really only had 9 months of exposure to the general public. The year or so before was licensees only and they enjoyed almost 101 access to engine developers.
On the other hand, Unity had years to build up their documentation resources due to longer public exposure, and to be honest, Unity did not change in 5 years as much as UE4 did in the last 9 months.
At the end what one uses to do their projects is a matter of personal preference, and if Unity does the job better, by all means.
But there’s no escaping C# in Unity, so replacing C++ with C# is not changing much in that regard. 