MUST be able to have SEO friendly URLs, without any hint of dynamic URLs.
We do use dynamic urls in our system but it doesn't make any difference to SERPS.
I agree that dynamic urls shouldn't make too much difference to search engine rankings on the major search engines. What might make a small difference is the amount of redundancy and dilution in a targeted url, the parts of the url that contain other things except the targeted keywords, and that can come in many different forms:
domain.com/targeted-keywords (no redundancy)
domain.com/c32-targeted-keywords
domain.com/targeted-keywords-c32
domain.com/targeted-keywords.shtml
domain.com/catalog/targeted-keywords
domain.com/websitebrandname-targeted-keywords
domain.com/targeted-keywords-bywebsitebrandname
domain.com/targeted-keywords-other-words
domain.com/category.php?category=targeted-keywords
domain.com/category.aspx?category=targeted-keywords
long-domain-name-with-no-relevant-keywords-in-it.com/targeted-keywords
etc
(it is a matter of debate whether some of the above examples do actually add dilution and redundancy or not, e.g. extensions like .html)
But if you've got your keywords in your url after the domain, that is good start, and the rest is just a question of squeezing out as much optimisation as possible.
So it is not the dynamic-ness of the URL which is the issue, it is the keyword dilution of the URL. Some systems might also generate static html versions of their catalogue in order to get around this 'issue', thinking that it really is an issue, but static html versions introduce their own problems, e.g. it is difficult to show dynamic real-time stock remaining numbers in a static page. Some ecommerce solutions generate static versions of their catalogues for other reasons, e.g. for better performance on cheap hosting since the database isn't being hit each time a page is loaded, I think some Actinic setups do it because they don't have an underlying database on the server.
Keywords in a url is just one factor out of the 200 or so factors that google use to rank pages, and in my opinion it is not up there at the top if you order these factors in order of importance and priority. Top factors are things like title tags, on-page content etc. This is one of the reasons why we haven't even implemented keywords in URLs yet within the ecommerce part (based on osCommerce) of our sitebuilder solution (although we have with the CMS part of our solution), but this is on our short-term to-do list, and hopefully when we add this our clients might see some slight improvement in rankings.
Hellsbells, by all means ask for keywords in urls as one of your requirements since they do provide some SEO benefit, but don't forget to include in your requirements all the other more important SEO factors too.
The other thing to consider, is that keywords in urls after the domain name, e.g. category pages and product detail pages, wont help much with the main keywords you are targeting for your site overall, i.e. the keywords where you want your home page to come up in the results. They only really start to kick in on the more specific long tail searches. So if you have say a fashion jewellery site, then your main sitewide keywords would be
fashion jewellery which points to home pages (so SEO friendly URLs after the domain name with keywords on other pages don't matter so much here), but a more specific long tail search, e.g.
Swarovski Crystal Bracelets will target pages within a site (so SEO friendly URLs after the domain name with keywords will contribute). The reason I use this is example is because one of quickshop's clients, bohofashionjewellery (another member of this forum) appears well in both types of searches, and that's with dynamic urls.
The only shop we failed to get to page 1 of Google was the osCommerce one but that was due to the highly competitive nature of 'designer clothing' and our lack of SEO knowledge at the time.
To the outsider, it seems like oscommerce is getting a bit of bad press on this thread, so I should say that it is possible to get SEO results if you
customise osCommerce right. For example, we have one client, ellemoda, who appear 1st page of google for their main site-wide target,
ladies designer shoes, and for more specific long tail searches, brand and product searches like
pure handbags ('Pure' is a brand)- and that's without any keywords in the either the main domain name or the url part after the domain name.