Hi there,
I think I can shed some light here and maybe answer your question in the process
I used to have a black 2000 accord. Black is just a bitch to keep clean no matter what you do. As for polymer vs. carnuba I think they way things are going today you can probably get a really good "wet" look out of either product but I think the carnuba has a slight edge over it. Try a combo of them like I did.
Here is what I found to be the best combo for my black accord. I used a product called blackfire Paint protection and polish. Although any polish will probably be good here. If you can get your hands on menzerna final polish I would opt for that over the blackfire sutff. Ok so here was the routine I used to obtain the best deepest wet look on a black car.
after washing I broke out my porter cable polisher and polished the entire car using the blackfire polish.
The next step was to apply the blackfire paint protection this is your polymer based sealant and will really protect your paint and not look half bad in the process it really adds depth to the paint.
Once that is done I toped it with a product called S100. Harley Davidson folks ought to be familar with this product. It can be found at your local Harley store and in my opinion is the best was I have ever used. goes on easy and comes off easy and really really gives the paint a brilliant shine.
Well that is what I did to get my car looking its best. Hope that this isof some help to you.