They're both good backlinks to have. And even though you may see lots of gray on the toolbar, Matt Cutts has given reassurance that "the Yahoo Directory has plenty of PageRank in our internal systems." reference [webmasterworld.com]
I gave up trying to get sites into dmoz years ago! I NEVER got a site in after the first year or so of designing sites, never got responses, half the editors were missing, some were allegedly bent... I've always been surprised google uses them at all.
They are both decent directory links to have, but are by no means necessary to get a site ranked well. I have only had one site accepted by DMOZ...probably down to a lack of editors. As for Yahoo, well I think it depends if you think that $299 a year for a link is good value. If you have a large budget for directory links then go for it; if not there are a lot of better value directories to submit to.
For anyone who managed to get into DMOZ during the early years, that good luck has no doubt had a long ride. For anyone wanting to get in now -- you'd be better off sprinkling fairy dust and chanting the magic mantra -- it will have about the same effect. So if you decide to make a submission anyway, do so not expecting anything whatsoever for a very long time, if ever.
I recommended my son sumbit him main company site to DMOZ he did and was accepted in about 8 months. Submit and forget if you don't want to do that no problem but sites are still being accepted, it just takes a long time to get in.
I've been asked this question several times and frankly I struggle with it. I lean on ROI.
DMOZ is quick to do, potentially valuable and I usually take a few minutes to submit within their guidelines. Granted, I haven't gained a listing in the last couple years but have managed to get some listed prior to that.
Yahoo Directory...IMO $299/year is really a company decision. If your business doesn't blink at that, then do it knowing it may provide little (if any return). I have sites doing just fine without a Yahoo Directory listing. I haven't been able to quantify the benefit/value but my intuition tells me it's becoming less important.
I'd love to get hear input from folks that have derived direct benefit from a Yahoo Directory listing - since it controllable and simply a money/ROI matter.
As for DMOZ, I submit and wait - with low expectations. Though (Reno) after reading your post I did check out some sites that are willing to sell me fairy dust, so I'll order up some of that and work on my mantra.
If you are the DMOZ editor for the region or locale that you live in, you can validly list your own site. Does your region section in DMOZ have an editor? Probably not.
If you're an independent business, go clean up your city/region listings. give yourself a nice link, give everyone else in your region a nice link too. Do a good job, everyone wins.
If you're doing SEO for clients, what I think you'd have to do is make the client do the account creation and editing, but give them the complete steps in order to get accepted - i.e. give them the URL to sign up, give them the text and URLs of the sample sites, coach them on how to be an editor and edit listings, etc. The client still has to be the editor to do this cleanly, but it seems that this would be repeatable.
Just submitting to the niche listings is likely to prove unfruitful.
That is good advice wheel except I would hasten to add one thing -- only become an editor if you are willing to make a commitment to the DMOZ purpose. DMOZ started out as a noble idea -- a free online directory run by volunteers, not by corporate employees. I think one of the reasons (no doubt one of many) that DMOZ has become such a mess is because SO MANY of their editors got involved just so they could list their own sites and perhaps those of their clients and/or friends, etc. Then they poop out and it's yet one more DMOZ category that goes months or years without any editing, which results in the kind of comments we've seen in this thread about the futility of even doing a submission.