Sitemap/SEO Question

I would say make sure that your product pages contain a healthy amount of unique content. If all they have on them is copy-pasted affiliate stuff, then I would say you could be at risk - however all sites are expected to have some degree of dup. content - for example if you embed a youtube video, that code is also going to appear on a lot of other pages. To be on the safe side make sure there's some other unique stuff on the page too.

I just wanted to add that it's important to remember that a sitemap, while useful, is not really an SEO tool. All your sitemap does it give the robot a basic roadmap of how you view your site, and the importance of that site.

ALL of this can be ignored at will. The sitemap does not help to correct canonicalization, nor does it assist in getting a particular page indexed and faster.

The issues that you are concerned about are for the most part mythical. Too many assumptions are made by people without actually data to support those assumptions.

What I mean is, for example, there is not such thing as a penalty for duplicate content, nor will a site be sand boxed purely because of duplicate content. However a site that has canonicalization issues could get sandboxed.

Basic logic would tell you that the idea that my our 2 sites, selling the same products are somehow duplicate content is just childish. If you need confirmation do a Google search for a very specific product. Any product, it doesn't matter. You'll find hundreds of pages of sites, many of which are amazon stores, listed amongst those pages.

The key to your site winning in the SEO game is going to be with a focus on site and link structure. Take care when interlinking, ensure that only a single page exists for each piece of content. There may be no penalty for dupe content, but there is filtering. This ensures that only the most authoritative version of that content is available in the index at any single time. It's one thing for another site to duplicate your content, its something else altogether having dupe content on your own site, and you're almost sure to get yourself filtered out of the result set.

To answer your specific question, the product page is the most relevant page so it should be listed. And since most people (excluding me) will suggest you don't have categories indexed, then its the only logical pages to have in the sitemap.

Have a think about what I've discussed here. There are ways and means to have archives, categories, pages, and posts on any type of site, blog or traditional website, and avoid any duplication internally. The end result is more indexed content. Google see's more indexed content in terms of the size of your site, and the bigger the site, the more authority Google gives you.

Having a Sitemap get's your site's pages indexed faster.

without sitemap it will be little bit difficult for SE to get index to your site and a website has a sitemap will be easily indexed by the Search engine bots