I have alwayes had some doubts about the supposed graphic quality of game engine
Can people really distinguish a Unity game from, let's say an Esentahl one ?
I dont think so
In my opinion the best engine is the one which allow you to get the same results in the shortest time
Developing time depend of course also on the famniliarity you have with the engine but , aside from that, there are big diffrenece

From my experience
Unity supplies the best editor
Leadwerks the best programming style