This is a topic I got heavily into back in October. Most of the other Uni horrors don't have any DVD issues (aside from low bitrates etc.) but Dracula has issues on every edition.

The 99 disc and 04 Legacy collection are almost the same, but the 04 audio is heavily processed and has a great deal of noise reduction applied. It is also missing the death screams at the end. The 99 disc is only missing a small amount of music from the end of the ballet scene.

The 06 Legacy DVD is artificially brightened, sharpened and does not look like the original film. The audio is processed but complete.

I personally watch the 99 disc, and have the LD on my wishlist (even though it lacks a PCM track).

I've thought about doing a version, but as TAF pointed out there are some unofficial and official 1080i and HD versions of the films floating around. It seems Universal did HD masters some time ago and are just sitting on them for a Blu-ray release. I've only seen a bit of the HD Frankenstein but according to others it looks like many if not all of the previous issues have been fixed.

And Bride of Frankenstein was just restored!!! Maybe we can finally see these on Blu! Still holding out for an ultimate Criterion boxset though.