I think that Slim lack the side protection. Earth and Patriot are colour changes on the standard pad. Highly recommended, I love mine and I've ridden a thousand miles or more in them without a chafe or bad wear, or alternatively those new Raceface ones which are a pretty good copy of the Kyle Straits.
D30 and similiar materials are good but they're not really needed here, conventional pads can offer great protection and don't lack flexibility/freedom of movement. Construction and design is far more important for kness than custard-tech as knee movement is so simple.