Yeah that's true - Stylus does require a DAW for playback, but you could just use something really stripped down (i.e. cheap).
I don't know about EZ Drummer - it may be a great program, Dave Swift obviously has more experience with both so can better make a comparison.
There are loads of great sounds in Stylus though - and the interface is awesome. The features are great - especially chaos and there's nice tools for shaping the sound to get what you want. It's easy, quick and diverse to get great results!
Like I said, EZ Drummer may be better - I just don't know that program. I'd go to a store where you can have a play around and see what you feel more comfortable with.
It's just for jamming, so ease of use is key.