I’m not up on online DVD cataloging, so I don’t know what the advantages of it are.
I use software called Movie Collector Pro from Collectorz.com to keep track of my collection. It works well. When I type the title of a new aquisition into it, it goes to a variety of sites (I find Amazon and IMDB to be plenty) and gets all the info on the film, including some artwork, and adds it to the list in alphabetical order. My only complaint is that I have to go back and edit the title if it starts with “The” and put the “The” at the end. Maybe newer versions than I own (4.8) have this fixed, but it’s a minor inconvenience.
You might want to look around for this software if you can’t find an acceptable online alternative.