If I really and truly could have only one bit for every horse for the rest of my life--- and there might be some damaged ones in there that made me want More Bit or Less Stability-- I'd want that double-joined, bean in the middle, D-ring to maybe have some copper or sweet iron in it.
I have 2 favs, my D french link, and my mullen happy mouth three ring, most horses go either or, the 3 ring is for me as i cant do any pulling on my hands but i like how i can adjust the reins to vary what the horse needs, ride snaffle or actually havent used the 3rd ring just second
Mind you i ride with light hands too and not yanking themin the mouth, actually rode a gelding who prefered the 3 ring to a plain snaffle of the same mouthpiece(i could ride him in the snaffle)
French link eggbutt snaffle. Can't think of a horse I've owned dating back to 1965 that wouldn't have done okay with that. Okay, I wouldn't have had good brakes on all, but would have had steering so what the heck. I'd say ' plain' eggbutt but in recent years most of mine have preferred the French link though they've been okay in a conventional snaffle.
It's not a question for me, since I do only have ONE bit for my horse:
a KK Ultra loose ring french link.
She does everything (jumping, dressage, cross country, hunter paces, trail riding...) in that bit.
I have borrowed other bits at times (Baucher, D-ring French link...) but this is the one she goes best in, by far.