Never used Kontact or EZ Drummer, but seems like it would be hard to beat Ableton Live Suite's combo of drumracks and stacking effects per drum sample... Do you have experience with both? Any reason I should look into the former when I've invested in the latter?
edit: Nevermind, after looking at Native's offering (Kontact), I can see it has a lot of advantages for a certain kind of music, but that isn't the music I'm writing...
I use Ableton and Logic and their built-in drum software often. They're both very good. When you want to program super real sounding drums EZDrummer and especially Kontact are unbeatable (and as another comment mentioned Kontact has libraries for much more than just drums). For me the reason I like contact is that the mixing interface for each element in the kit is really easy to use and tweak. Besides that the samples are phenomenal. Another option that may be more relevant to you is NI Battery [0]. Personally I just like to experiment with different options as I find that the simple fact of working in a different UI will result in different creative output.
Thanks for the comment- I was hoping to hear about why you prefer using a 3rd party drum machine in a DAW. For the time being, I record or find all of my samples so I'm not particularly attracted to the kits. The interface looks great however. I probably won't use it anytime soon, but it does appear to be quite powerful.
Battery would be a closer competitor to Ableton's Drum Rack. It also included gigs of samples from 808, 909 to heavily processed sounds and percussion. The included samples are about equal in quality to Ableton's, but Battery includes built-in FX and routing for each sample. So you no longer need to add a compressor to each sample, and an EQ, etc. It's already there, as well as effects like emulations of older sampler hardware. The downside to Battery being that it's more cumbersome to add effects which aren't already included (you need to route them to a separate output, and depending on your DAW process it on a new track).
Geist2 and Nerve are some other closer commercial quality alternatives, though I don't have firsthand experience with them. Ableton's Drum Rack is really fantastic though, and also pro quality.
Kontakt is a different beast. It includes it's own scripting engine and can easily create multi-sample instruments with different randomly chosen samples or samples chosen based on velocity or note (or both). You would use Kontakt to create a realistic sounding drum kit, or piano, etc. Things that you don't want to sound sampled. EZDrummer / Superior Drummer are similar, but specific to drumkits and you can only play with the included packs/sounds.
Kontakt is pretty cool, not just for drum machines but any samples. For example, the NI orchestra samples are absolutely amazing. For drums it's just another sampler, you're probably better off sticking with Drum Rack unless you want the specific samples offer d by Kontakt.
edit: Nevermind, after looking at Native's offering (Kontact), I can see it has a lot of advantages for a certain kind of music, but that isn't the music I'm writing...