I think you should continue to use Unity to focus fully on your game.
Choosing another tool will cost you some time to learn it.
Hi wesley, thanks for your answer, hmmm actually that's not a problem for me, I already know Unreal a bit. And I think I will end up using it eventually, because I also have future plans to make a 3D game and I probably will not acquire such visuals with Unity as with Unreal. So, it will be a good thing to me to make a simplier game with it first. :)
Edit: Hmmm, I see there is quiet huge lack of 2D platformers tutorials for UE4, so maybe will go with Unity.