I'm in both.
Disbrides is specifically for Disney weddings. It been around for years. You cannot join unless you're a Disney Bride (or groom). It was beyond invaluable when planning my wedding. The reason it's only for Disney wedding couples is because a Disney wedding is so specific and different than planning a "normal" wedding. DFTW isn't the greatest with straight answers, but these ladies can tell you exactly what's up from experience. No advertising or vendors allowed. Wedding talk only. There are a bunch of spin offs for non-wedding talk.
Disney Bride's Diary is for Disney weddings, Disney inspired weddings, Disney fans getting married, etc. They're all inclusive and you'll find every type of bride out there, but with a Disney flair. I found this group was much like many other bride communities out there, but Disney-fied. Much younger than the other group but much larger from being so inclusive. Will have some Disney specific advice, but lots of general wedding advice. Allows advertising and vendors to join. Non-wedding talk allowed.
You can join both or pick which is best for you. If you need a link, feel free to PM me. But don't let one of the above groups scare you out of the other. Both groups have their specialty and are full of really great ladies.