Definitely FQHH as that is really the only part of the horse that's used for jackets. No other part of the horse is usable for that purpose. Whether the hide ends up grainy or smooth is entirely up to the tannery and / or jacket maker. Aero's chromexcel FQHH is very smooth to start because the hide is run under a glazing jack, high pressure glass rollers that smooth the grain. Other FQHH start out very grainy.
Is there any reason, beside aesthetics, that this process is used? Does it have any effect on the durability and general quality of the leather?
Oh, I guess this means that the Vicenza leather is also FQHH? That's really surprising, since it's a lot thinner than normal FQHH... How is that done?