A while ago a woman was wondering which "Full Cheek" snaffle bit to choose for her horse. I am new on HF and thought I would post but the thread was too old. Here are some thoughts when choosing a snaffle.
When choosing a bit remember that the narrower the bit the stronger/sharper it is in a horse's mouth. In dressage we have a 14mm min limit diameter for use on dressage horses. This rule is meant to protect the horse's tongue and bars from many of the newer very narrow bits seen today. My favourite inexpensive full cheek is the JP by Korsteel bit here is an example; JP by KORSTEEL - Full Cheek SS Mouth - 6 | eBay
I like these bits because of the anatomical curve designed right into these bits. The JP bits lie beautifully in the mouth, over the tongue and bars creating an even pressure, when the reins are used. This feature may eliminate the need for a three piece bit as the bits' curved design, discourages the palette pressures. However if you have a horse with a very flat palette, JP also makes three piece bits. The thing to remember about the three piece is the width of the middle piece and the fit of your bit. With a three piece bit you now have two joints in your horse's mouth versus a single joint with a plain snaffle. If you look while a three piece bit is on a horse and open its lips up, you will find that you don't have to pull a bit very far, and one of the joints will slide across the tongue and rest on the bars at the side causing a painful pressure point there. So it is important to choose a bit that fits snuggly (except in a loose ring) without pinching, to the horse's lips, to prevent the bit from sliding much in the horse's mouth while in use. In other words the shortest middle piece possible, and the fitting is more precise with a three piece bit. As well the Dr. Bistol's with their big flat piece in the middle puts a lot of pressure across the tongue, and if not fitted perfectly almost always have one joint or the other pressing into the bars. As for rubber and plastic bits, well that depends on the horse. For horse's that fidget and play constantly with a bit, clammering them against their teeth, the rubber and plastics are often just the cure to quiet the mouth. We had a pony with this issue and it cured her after years of playing and clammering, almost immediately with a simple plastic bit. This is my most favourite expensive three piece bit, it is the RS model by Sprenger curved cannons, turned joints to lie flat on the tongue and a very small lozenge in the middle, just perfect! It also comes in full cheek, and loose ring models. model; New Herm Sprenger DYNAMIC RS "D" RING SNAFFLE 14MM | eBay