Have to say here that Glory bits are a unique mouthpiece, not a mullen or sweetwater, because of the angle they are set on the cheeks with. I haven’t seen any other bit mouth like that, on any kind of cheek pieces made by anyone else.
So if you think you want a Glory bit, you have to buy a Glory bit, with the cheeks you prefer. If you want a mullen mouth, that is NOT a Glory bit mouthpiece. Similar as the mouthpieces look, they do different things in the horse mouth. I would say they are NOT interchangable in getting your expectations/desired results from a horse, though the same horse could wear both bits and go along all right in both of them.
When I first saw the Glory bits, I was quite intriged at the design. I liked the combination of the mullen width and the bars of the sweetwater for tongue relief. However for the kind of horses we ride and drive, I just didn’t care for the engineering. I want my finished horses to end up going with nose on the vertical part of the time, both ridden and driven, while the Glory bit would be working against me for that. This is because the bit will never hang vertically by it’s own choice, with the offset mouthpiece. Cheeks are never naturally vertical. I also didn’t care for the heavily copper base metal in the mouthpiece, for the same issues of using copper mouthed bits.
To test for bit hanging straight, you lay the mouthpiece over your hand, shank sides hang straight up and down. Weymouth of a double bridle is one of these kind. Western bits used to have MANY kinds of cheek/shank designs for various reasons. We always tested a bit for how it would hang in the horse mouth before purchase. No use teaching a horse to hold his nose vertical if the bit bites his tongue because it was weighted to hang straight on a horse with their nose out!
Glory bit was originally designed for Morgans, with the low palate, thick tongues, and at the time, thicker throatlatches. Bit has been around for a while! It did seem to be the miracle bit for Morgans for quite a while, they went happily in it for many reasons. Now the Glory bit has been more widely used by other breeds, still makes a lot of horses quite happy to wear it. Just pointing out that the Glory is built DIFFERENT than other bits for a reason, not interchangable with other mouthpieces at the higher skill levels.
If a Glory works for you and your animal, go for it. But as GTD and RAH said, start with less bit, see if animal is responsive to the snaffle. If not, then you can move up to a leverage bit to train his responses better. Then maybe then back up rein setting to just rough cheek or the ring beside the mouthpiece again. Beginner horses often don’t understand bit very well when lessons start, so bit setting is stronger on them to just maintain control. As they improve, you can often reduce the setting. You have to train a mouth on your driving horse, same as all his other parts! He has to learn to give and take, not hang on your hands. You have to “fling him away” at times as the reward for “giving” the tiniest fraction so he can feel the differences FAST and learn from it! I want a horse with a “trained” mouth, not something with a fake “soft mouth” that over reacts when you touch the reins and flings their head way up!!
I’ve been on the hunt for a 5" one for a while. My cob mare prefers it to a snaffle by FAR. They just fit the mouth so well. I hate that my bit collecting habit is growing more and more expensive. I miss those $25 snaffles…