Convertible top care

So, z31maniac's thread about detailing products for his new-to-him Miata got me thinking about convertible top care.  I have two which I haven't ever thought about specifically treating.  There were some positive comments about 303 products, and I'm thinking of heading that way, but I have a few questions for the more experienced convertible people.

For background, my cars are an E46 M3 with a cloth top and an NA Miata with a later NB (glass with defroster) vinyl top.  The BMW is starting to get a bit rough in spots, but it's got a lot of life left.  The Miata is in quite good shape.  Both cars have seen only bucket-of-suds-and-a-garden-hose cleaning while in my possession the last few years. 

Questions:

The tops are both black, so cleaning is desirable but isn't the highest priority, preservation is.  Is there a product that is good for sealing/preserving both cloth and vinyl tops?

If not, what are the preferences for cleaning/sealing each type of top?  303 has different products for each top type.  Should I just go that way?

there is/was a product called ragtop cleaner. I used it with a very soft brush on my Vettes white top to good results.

303 is OK, but what you're really looking for is the RaggTopp juice from Wolfsteins. I've used the cleaners and protectants on both the vinyl OE top and canvas replacement on the S2000.  Never had a fading issue with either material, and once well-cleaned and treated the maintenance was super easy!