You always ask the tough questions. Of our 2 sites, 1 is DMOZ listed, one is not. The one that is listed has an easier time attaining top SERPs, but it is in a less competitive field. The one that is not listed is the one that was having trouble getting crawled since our restructuring. Both are doing well now, but it's taken a lot more work on our non-listed site.
I guess the answer is both. Creating an XML sitemap didn't take long, so that's a no-brainer to do. DMOZ has been waiting on our site for a
very long time, and it's not guaranteed to ever be listed (although cbp says it is still in line to be looked at.)
I don't think you can easily say one or the other is more important. It's sort of like asking if having content or getting links is important. You need content to get the links. In this case, you need to be indexed to be ranked, and the DMOZ listing will just give your ranking a nudge.
I couldn't tell you how many sites have asked me to do
SEO for them and I find that they have 3 of their 1000's of pages indexed. Without indexing,
SEO won't help. Links can help indexing, but not nearly as fast as the sitemap. I'd say step 1 for me is now an XML sitemap, step 2 is DMOZ (submit it and forget it), step 3 is other directories, and step 4 is additional link building. Of course, on-page for Yahoo and MSN has to fall over the top of every last one of those, because content building is a continuous job.
Brian.