TB jumper - mulen mouth pelham b/c he has a VERY sensitive mouth, and responds best to the mullen and likes the pelham. He actually gets very mouth sore in a simple single jointed snaffle b/c he has a low soft palate and will run through a simple 3 piece bit. He's quite happy in the pelham, and I prefer the added level of communication (note: NOT control, communication) that I have with the double reins when doing jumpers.
TB jumper mare full sister to the above gelding - also very sensitive mouthed but prefers a single jointed snaffle as opposed to a mullen as she will lean on a mullen. She goes very well in a loose ring happy mouth and although she can get strong, she responds to seat and leg very well.
Arab gelding - eventing, formerly a race horse - cyprium french link b/c he's learning to accept the bit rather than brace and lean on it. I'm also spending a lot of time riding him in just a halter and lead to let his mouth relax as he adjusts as he's a new rescue.
Dressage TB gelding - full cheeck snaffle, because he gets stiff in the neck due to past back injuries and he doesn't need anything more than a snaffle. No keepers on the full cheek, he's very soft mouthed and once he's back in better shape I doubt that he'll even need the full cheek since he's been seeing the chiro regularly for years and is ready to finally be back in work! (another horse reared while playing and fell across his back with all 4 feet off the ground in turnout, and then after recovering, he reinjured it in the field)
Clyde/TB cross - eventer/field hunter - Loose ring happy mouth b/c while he's big (17.2 almost 17.3, and about 1800 pounds), he's got a soft mouth. When in the field, or for XC, he'll go in a 2 ring elevator hapy mouth so that I have the added control of leverage since he's still got a soft mouth, but when he gets excited, and 1800 pounds wants to go that ---> way, you go that ---> way lol! The 2 ring elevator helps me say hey! Dude! I'm still up here and we need to turn now!!! Though in stadium he's fine in his loose ring. On occasion when he's strong, but I want something between the loose ring and the 2-ring, i'll use the loose ring happy mouth with a balanda noseband. I got it on sale and it's by CWD (LOVE their leather) and it's basically a padded smaller/softer version of a crank for field hunting, that has 2 pieces of elastic that go from the front center of the noseband to each ring of the loose ring bit. When I pull back, it adds a little nose pressure to again help him remember I'm still riding! It's a nice midway b/t the loose ring and the 2-ring bits.