The most important thing to remember when you change to a shanked bit of any kind, is to keep your hand soft. Go with as severe a bit as you need, but remember that in Western you don't have that same full contact as you do with English. Ideally, you work off leg and rein pressure on the neck, not the engaging of the bit.
I always suggest that you look for a bit with tongue relief. Mullen makes great bits for that. My boy likes a medium port with a roller.
I have found that it takes a horse four or five rides at least to decide if they like a new bit or not. My boy threw a hissy fit about the first dozen rides with his new bit... I was going to change it back to his old bit, but then I started having trouble getting him to wait until I was ready to put it in his mouth. Nowadays I have to make sure that I am holding the bridle at the ready before I get to him because as soon as it is in reach, it is in his mouth.