Of the types, type A is the original (and the most expensive to manufacture), and still has some advantages over the other types. Type C is the least expensive, and has the weakest cross-links and if not held to high quality control, can be brittle on the outside. Type A has the strongest cross-links (and is linked with carbon atoms - the others are a hydrocarbon link), the shortest bend radius, and is the only type that can safely be restored if you kink it. On types B and C, if you kink it during install, you are supposed to cut out the kink and insert a coupling. But, with type A, with a heat gun, you can restore it to the original strength and shape (if you've been trained and know what you are doing). Timewise, and cost, I'd guess it's sort of a wash on that repair, but one of the big things with pex is minimizing the connections, so I think it's worth the time to relieve the kink. Better yet to avoid getting one in the first place (and that's easier with type A, since it is more flexible than the other types).
According to Uphonor's website, they've installed over 2 billion feet of pex in the USA and over 12billion feet worldwide. that's enough to wrap roung-trip to the moon, twice. That's a lot of miles of the stuff, and they've been making the stuff for nearly 40-years. When you add in the other manufacturers, there's a LOT of the stuff out there.
There ARE differences in the available tubing. Whether they are important to you or not, would depend some on what you are doing. Consistent quality is the biggest issue, and that could be a problem on any, but is more questionable on the price leaders.