SSD's feature set falls somewhere in between EZ, which is intentionally limited, and Superior, which is meant to offer the ultimate tweakability thing.
Slate just goes for ultimate realism these days. If it doesn't sound like a real drummer drumming, it isn't working and isn't going in. The legacy libraries that come free with SSD5 are more "mix ready" and processed, but lack that ultra hyper realism that the new kits and pieces have. The mixer in SSD5 is what I'd expect to see from a well-miced and tracked kit, so if you're comfortable with that, you'll be golden.