It's hard to say what is best in your situation without seeing the horse.I always ride with a quarter inch POW regardless of the horse I'm on. I find I rarely have to use them tho.
If you're horse will not move forward and we will assume he was trained properly and understands your aids, then there is a respect issue.
Until you take care of that respect problem, it doesn't matter kind of gear you put on as he won't care about them.
Straighten out his manners and you guys will be well under way.