If those are the best two options you only have, I would go with the KJW. M&P9 might be light but since its WE, I would stay away from it. Having said that, KJW will have the compatibility with TM parts as well as you can use two types of mag system. Either C02 or Green gas. Go to a local store, look at them, and have a feel for them. One is slightly slimmer than the other. It then becomes individual preference. Good luck!
MODT - tu fui ego eris