It sounds like you guys have made a bit of progress working on your game in Unity, but are not too far down development if you are considering porting over to UE4. One thing I would recommend you keep in mind if your team decides to switch over to UE4 is that it will take a bit of time to get accustomed to using the engine, especially if you have not used any versions of UE prior to now. For example, when I first started using UDK it took me about a month of following tutorials before I was able to really create original content that worked the way I intended it too. Just something to be mindful of whatever you all decide.