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Fellow Audi-nut here, and I expect my LSPs to last *at least* all through any tough winter. Short answer: FK1000P. Just get that and be happy. Seriously
Collinite is good stuff. Many sealants don't last nearly as long as Collinite, and 476S outlasts 845 by a considerable margin IME. I use 476S on my '93 Audi, but for very specific reasons and it needs redone a *lot* more often than the vehicles with FK1000P even though those get used a lot harder.
Heavily layered KSG (at least six layers) lasts longer than Collinite. FK1000P rivals the heavily layered KSG without having to do *nearly* as many layers.
For durability in a conventional LSP as opposed to a coating, I'd put FK1000P up against anything, which is probably the main reason why so many of my vehicles wear it. On white it'd be a complete no-brainer for me (it's what I used on the white Crown Vic daily driver I used to have). At some point I suspect that I'll switch even more of my vehicles over to it.
BFAFPP looks very carnauba-like. It darkens colors like Audi silver too much for my taste and isn't very durable IME, certainly not something I'd use for winter. Eh, it's NOT something I'd choose for a white driver period. Ditto for 4-Star UPP (which I'm still using on the S8 despite its terrible lack of real protection against etching).
Back where I started- just get FK1000P. You might consider spritzing it with FK425 after each wash as a drying aid, the two products work nicely together.
EDIT: rather than claying, I'd do a proper decontamination with ValuGard's ABC, especially on a white car.