I own both instructional DVD's Bravo and Drysdale. I have actually spent months studying them both thouroughly (Yes, actually taking notes, watching the DVDs countless times, drilling the moves and incorporating them into my game) and I must say that both offered me extremely helpful tips for my ground game.
My background as an elite competitive gymnast allowed me to take to rubber guard like a duck to water. If I were to contrast Drysdale's Rubber Guard vs. Bravo's, I must say that Eddie is a lot more parsimonious about his approach and he teaches each one of the movements in the sequence. If anyone takes the time to study it meticulously, it is actually extremely insightful and cool. Drysdale on the other hand takes the so-called "boring" details out of the equation and he teaches you many techniques that work efficiently from the rubber guard. For instance, Bravo will teach to go from Mission Control to Retard Control, then from there you might go to Crackhead Control. From there Bravo suggests you should always first clear the head with the arm opposite from the leg that's controlling the opponent to transition into omoplata, gogoplata, or spiderweb. Drysdale throws all that step by step approach away and he teaches that one can clear the head directly without even going through those steps. Bravo would tell you that when one does that, the success rate for transitioning to another move or submission decreases a lot.
That being said, I have learned so much from both instructionals that I now see Drysdale's approach to the rubber guard as an important evolution of bjj. In fact I had a very interesting anecdote that involved the rubber guard. When I started taking private lessons with Soca Freitas, he was evaluating my guard, etc. He was passing every one of my guards (closed, butterfly, half) like nothing. Then I figured I would throw in the rubber guard for good measure. He absolutely was not expecting me to do it and he was laughing because I used Eddie Bravo's set up to Mission Control and then from there I used a Drysdale technique and sunk in a reverse triangle from rubber guard. He thought I was setting up a regular triangle but in fact the reverse triangle worked beautifully and Soca gave me his usual "Nice!!!!".