Why are these two products even being compared? They have almost nothing in common, and are made for two entirely different work flows.
Stevens products are extremly processed, ready to go out of the box, and are made for very specific genre's. Articulations, velocity layers, and mic choice are lacking in a big way however, and his drums have a very signature sound, but that could be a plus or minus for some people.
Superior has either completely raw, or lightly mixed samples, that often require some time to mix them, (Metal Foundry is raw). This of course allows for the creation of almost any tone however, so if you are confident with your mixing skills, there is absolutely nothing stopping you from making them sound almost exactly like SSD, or anything else you can think of. Superior has the advantage of realistic micing, and articulation choice as well, so you can create a more realistic drum track.
To me, Superior is more versatile in tone, and articulation, but requires more effort from the end user to achieve their desired sound. SSD will allow for instant gratification, but wont give you the versatility, or realism.
For what it's worth, I don't think many of the Metal Foundry demos sound good, nor do I think SS drums sound good. Both are entirely too processed IMO, and I honestly can't stand the over processed, triggered drums in most metal recordings (I understand most of you probably feel the opposite there). I do know that Metal Foundry is raw however, so I can process them the way I like, use them in any genre I like, and will be avoiding the presets as I always do.
/2 cents.