You basically just have to look at your horses level of training, any problems they have with their current bit, and what you do with them. Just try a bunch of different ones to find the right fit for them.
My gelding goes in the D ring or loose ring versions of the Stubben EZ control bits which are double jointed and lock in place if the horse tries to lean on it. Those are his day to day bits. And I occasionally will use a hackamore combo bit on him if he hasn't been ridden in a while or if I go galloping.
My mare who is very well trained can go in a simple single jointed D ring because I don't need to touch her face much at all. I don't love single jointed bits usually because of how they break in the horses mouth and can pinch, but if your horse doesn't need to be touched in the face they're fine.
For my mare I use a eggbutt snaffle, I trained her this way and all other bits are either too harsh on her, or I just don't like them. My gelding has a French link, he was trained with this one and he seems super happy with it so I never changed it.
A few days ago I started riding with the elevator bit.
Since I started to ride the horse I'm jumping with I always used a Pelham, but he started to be really energetic so I couldn't ride him on the right lead and of course not jumping him properly. So my trainer and I thought that changing the bit could be helpful.
We worked some horses before with the elevator bit and we thought it could be great also for him and... it worked!