I'm new to the site and just tried 303 and Vinylex for the first time because of the recommendations I've read and, how's this for a "poltically correct answer", I like them both! (for different reasons):
303 - for the interior, on dash, doors and leather seats too! Gives a slight satin sheen, nothing slick and greasy. Doesn't attract dust.
Vinylex - on the tires, and I must say that of all the tire dressings I've used I think I like the Vinylex the best. Gives a nice satin sheen. Just what I've been looking for. If you want the "wet look" then Vinylex isn't for you.
Just my opinion but I wouldn't use Vinylex on the interior and I don't think 303 gives enough sheen to the tires.