Does the layout of the page really help prevent duplicate content penalties?
Duplicate content isn't really penalized... Traditionally, at least, it's been filtered, and the site with the highest PageRank usually wins. The layout and design should not affect dupe content issues... html text content is what Google looks at.
That said, if you decide to go with the two sites that are both intended to rank, do make the sites look as different as possible. You're doing this for the consumer, not for Google. If both sites rank and a searcher sees both, you don't want the sites to appear related.
If you manage to get a large enough percentage of unique content on your pages, and get good inbound links from sites independent of each other, there is a chance that both sites will rank. Separate hosting also can help. Google doesn't want to rank sites selling exactly the same product lines, unless the sites serve clearly different purposes.
A variant on the not-indexed distributor site might be a distributor site that is indexed, but is optimized basically as a support site. It might rank well for product documentation, which would be a refreshing change if you've ever tried finding such materials among current offerings... and you could have log-ins for distributors to check prices, etc. This assumes that the distributors know where the site is.
There are variants of this problem, btw, each with a different twist... manufacturers who don't want to compete with their distributors (neither sells direct to consumer), manufacturers who do compete with their affiliates (and both sell direct), companies that have franchises in geographically limited territories, etc.