Preference? Holmenkol runs $50 and treats 2 spins; Aerospace 303 is $15 and will treat probably 10+ sails. I treated sails with H in the past and noticed they are more slippery but not sure how long that lasts. I've used the A303 and its slick as snot and it brightens old colors as well. A303 is not a water proofer and H is advertised as such. over the last week, I treated 2 sails with H and 1 with A303, I'll post some results as they get sailed.

important! don't treat your trampoline with A303, don't ask me how I know. Tacking! whooooosh! splash!