Riders that have had experience bringing along may different types of horses usually have a short list of favorite bits they like to use, depending on the horse and the situation. I've had pretty amazing luck with double jointed loose ring snaffle bits, such as a French link or an oval mouth. I like these because the are generally great for communicating to the horse what I want, don't have that nutcracker action of a single jointed snaffle, and overall just seem to help reduce/eliminate tension when used correctly. They are a very basic, "soft" bit, which lets me gauged whether or not they'll need anything stronger or different. These bits are my baseline. I put Soon in a copper oval mouth (just like the one pictured) to start off with. He seemed to do very well in it - he was soft and responsive, and didn't seem tense or grind the bit at all. I was pretty sure I nailed it on the first try (self high five!).
Having seen practically the entire barn in the Happy Mouth brand of bits, though, I decided it was worth a shot. Happy Mouth bits come in all types, but are plastic covered and are usually flavored/scented with the idea it helps the horse accept the bit better. Feeling like a bad horse mommy for not getting one earlier, I bought a double jointed, loose ring snaffle Happy Mouth thinking that I was going to make Soon happy. Aaaaaaaand not so much.
Long story short, he really seems to like that oval mouth (hey I nailed it after all, high fives for me!). Not sure if he likes the wider, heavier bit (which the oval mouth is compared to the plastic covered bit), but he just seems softer in it. Part of it is that he's continuing to learn and understand what I'm asking, and is just a naturally soft horse to ride. But there's just a little less tension, a little more give with him in that oval mouth. I call it the "wonder bit" because I've had everything from big, rambunctious, unfocused horses, to smaller and more ride able ones do great in it. So I'll keep the Happy Mouth around just in case, but for now he's good in that oval mouth. I'll keep that on as long as it continues to work for him.
Not that I've really had to touch the reins very much, because he's just a beautiful, wonderful, amazing genius.