I have both aswell, If i where to sell one of them it would be the YFZ
Dont get me wrong, the yfz is def a fun bike to ride, good torque/power handles great etc but for me the banshee is where its at.
You have to think about which bike is going to suite you better, and then go from there.
If you are looking to get into mx and gncc, I think you are in the right direction looking for a YFZ, but if you can swing it and keep both, I say do it, dont sell the banshee.