If you are pleasure riding, a well trained western doesn't need a bridle. Just a halter and lead. But if you are showing in western a nice Tom Thumb or o-ring snaffle. Depending on the class you are showing in. I actually know a young girl who rides an Arab gelding, in the field with no saddle, bridle or halter. She rides down the road in just a halter and lead. She's 7yrs old
I have always had great experiences with the snaffle. I used that on my best barrel horse. I also used the slide and gag on a less experienced horse to gain more control while training. I would recommend the snaffle on an experienced horse. I would use a loose-ring or an eggbutt, depending on what kind of riding you will be doing.
Snaffle bits are made for direct reining, curb bits are made for neck reining. In a show ring any western horse over 5 must be in a curb. For just pleasure riding, it doesn't really matter. Whichever your horse prefers that you don't need a lot of pressure with. I used to trail ride a saddlebred bareback and bridleless.