I have started using UE4 now.
Blueprints is a visual node based way to create games (or supplement your C++ code ).
The current version of UE4 (4.10.1) requires VS2015 for a C++ project BTW.
Bits and pieces from UE3 are not (currently) part of UE4 due to licensing conflicts (SpeedTree, FaceFX, And possibly more).
Unity apparently supports 3D mice, Wheres UE4 currently does not (One EPIC Dev is doing something in regards to that but it seams that it is not officially on the road map and higher priorities and what not).
Other then that I can't say much.