>It would be nice to know so I don't (and many other owners of Vacation Rental websites) don't have to waste their time submission requests within this forum.
Start by reading the category description. Vacation rental sites should be submitted TO THE LOCALITY CONTAINING THE VACATION RENTAL.
Vacation rental DIRECTORIES should, again, be submitted to the proper subcategory.
The usual caveat applies: small directories need to be very very focused to be useful to surfers. The chance of a global directory appearing with enough unique content to warrant "comprehensiveness" at a top level is below zero, for surprisingly small values of zero. So, yes, I'd expect all new listings to go into the regional subcategories.
A rule of thumb: within that focus (usually geographic) they should show unique content, size and comprehensiveness at least comparable to the ODP, as well as evidence of continued support -- we know how much effort it takes to keep a directory from going stale. 99.99% of the "directories" on the web won't measure up to the current standards. (In fact, the ODP doesn't measure up to the current standards.)
Another rule of thumb: directories are only useful when the user has to look through fewer listings (on the average) to find a specified site, by going to the directory sites FIRST. Obviously, the ideal is to list all the websites in the ODP, and not list any directories -- that way, the user sees all the websites once in one place. And the worst possible situation is when there are many more directories than sites ... as in Orlando and Las Vegas. The surfer has to look through much more content just to get the same information -- that's why we keep saying such directories are worse than worthless: every single one removed from the web makes the surfer's job easier!
So the second criterion is: looking only at the directories that are LARGER than yours, how many listings do you have that at least one of them doesn't have, and how many of their listings would the surfer have to go past (starting with the largest directory first, of course) to get to your content? If the answer is "several times more listings than there are actual websites to be listed", then your site is probably not worth listing -- we'd do better just "mining" it for links, then discarding the husk. If the vast majority of its sites are already in the ODP, then it's not worth mining.
With this in mind, rather than spamming the Directory category with small paid-classified ads for individual property websites, my recommendation would be to offer (as part of the services that come with sold listings) submittal to the PROPER category of the ODP, which will usually be a locality, and will often get a quick review. (There are exceptions: Orlando is a dismal swamp of doorway pages leading to directories leading to blind lead generators for agents for directories of doorway pages ... legitimate sites with unique content (such as actually offering a unique house they actually own) tend to get buried in the muck. But for the most part, submittals to the CORRECT regional categories tend to get listed fairly quickly. And correct placement of submittals is a genuine service you can offer individual webmasters, who usually think submitting to the top level of Vacation Rentals is a Real-Clever-Idea, and (since they only have one site) won't learn better soon enough to be of any use to themselves or to us.