I broke my Paso mare in a D-ring, she rode out nice, but she is a very goey mare and I didnt have the brakes that I wanted with her. I made a small step up to a tom thumb and have never looked back. My thought is that most pasos, walkers, QH, whatever.... are ridden in a particular bit as dictated by tradition, moreso than function. I have ridden horses of all types that didn't respond to a certain type of bit. You may just have to sort through a pile of bits and find a middle ground that makes you both happy.
I will say that my Paso mare is the most finicky horse I have ever dealt with in regard to tack changes, I assume that, this is more an idividual thing, than a breed thing.
Tack selection has to be driven by two factors: First, the requirements of the discipline
. In the formal disciplines (Dressage, Fox Hunting, historical re-enacting/living history, etc.) you must meet fairly strict rules. In the less formal disciplines (trail riding, Cubbing, Mounted Shooting, etc.) you can have a lot more lattitude. Second, the needs of the horse and rider.
Some might put this first; I put it second. In any event, whatever is chosen to meet the rules and the needs of the horse and rider. Compromises between First and Second might well have to be made.
Jim makes an important point when he observes that a lot of what is done is driven by tradition vice function.
Further, what works in one venue might be really worthless in another. As an example, if you're competing a TWH in a flatshod rail class you might select heavy shoes, up to 48 oz., to get the gait quality that will take home a blue ribbon. Yet to use such shoes on that same TWH and intend to cover 50 miles in an Endurance competition would be monumentally stupid.
Smart horsemen apply the rule of "horses for courses." The same principles apply to tack.
As to Paso Finos, the show lines in that breed can be a challenge as they are bred to present a very firey appearance. A level of finickyness will go along with this.