I use traditional pit-tanned English bridle for many of my belts. Bridle was originally developed for equestrian use, it's a durable leather with dense fibers. My bridle is hand-finished with a waxy topcoat, which I like to leave intact, so each hide will come with a different degree of waxy "bloom" on the surface. This will wear off naturally with time, or if you prefer, it can be buffed off with a soft cloth. Bridle starts out stiff, with a smooth grain surface but breaks in nicely, softening at high-wear points and developing grain texture as the leather flexes from use. I prefer to leave the edges of my bridle leather undyed, showing the natural contrasting color at the center of the hide.
Chromexcel (CXL) is a chrome-retanned or combination-tanned leather. It is both chrome tanned and vegetable tanned in order to benefit from the best of both methods. Chrome tanning creates a supple, buttery leather with improved weatherproofing. Chromexcel is traditionally used to make footwear.
Natural chromexcel bears a somewhat confusing name, but in this context "natural" means that the leather doesn't receive any pigment in the tanning and finishing process, so the unique shade of natural chromexcel is created by the addition of fats and liquors, not dye.
Reversed natural is simply the backside of the natural leather. It can vary in shaginess and color from hide to hide.
Black chromexcel is slightly less glossy and more satin than black bridle.
NATURAL VEGETABLE TAN
Natural vegetable tanned leather is a blank slate for honestly-acquired character. This leather is undyed and minimally treated in the tanning process. If you enjoy watching your leather age and patina, this is the choice that will provide the most dramatic results.