I ride Vega and Montana in a Myler Low Port Comfort Snaffle Eggbutt
When I got Vega she was ridden in a single jointed Kimberwicke and would toss her head constantly. I went to a local tack store, told them the problems I was having and they recommended a slow twist loose ring. I rode Vega in that for about 5 min and took it out. She was worse then before!
So I decided to take the bit into my own hands and started researching stuff. I found that a single joint creates a nutcracker action and that most horses don't like this. So I figured that was Vega's problem and was no on the hunt for a double jointed bit.
I came across the myler bits and loved the concept behind them. I did as much research as I could (including e-mailing them to try and figure out which bit would be best for her) I decided that a low port would be good (to give her some tongue relief) I also liked that it has independent side movement, so if she drops a shoulder, I can lift that side of the bit. I also liked that it has copper inlay (which helps to relax and promote salivation)
As soon as I put that bit in Vega's mouth and rode her, she was great! No more head tossing and she would whoa when asked as well as turn very nicely.
Then I got Montana. I believe he was ridden in a correctional western bit. Being an english rider, I knew I would need something different and used the myler on him, to see if he needed something with more or less tongue relief. He is doing fantastic in that bit. I was told he can get strong on trails and would need his western bit, but I took him out on a 4 hour trail ride in the myler and he was an angel! I am very happy with my purchase (I believe it cost ~$80 and well worth it IMO)
I don't use a bit for Gem. I ride him in either a rope halter or his leather one. When he did have a bit in his mouth, it was a Tom Thumb, which I hate so I don't use it.