Hey Steve!
Battery is a very nice sampler. Addictive Drums, Superior Drummer etc can't import it's own samples but are great for tweaking the sounds in the sound packs and treat them like "normal" drum tracks. Session Drummer and BFD can import samples but are limited in tweakabillity compared to Battery.
Battery is a different beast, well tailored for not
just playback of samples, but also sound design of percussive sounds. It can also import loops and rex-files, map them out over the pads with great playabillity. Think of Battery as a relative to Kontakt while Supperior Drummer, BFD and such is are closely related to a real drum kit
I use Superior Drummer for accoustic sounds, which it does great! And for everything else I use Battery. I work a lot with sampled sounding and electronic drum sounds. I throw random accoustic drum sounds into it when I need something that SD doesn't provide. And for electronic drums, sound effects (one shots) and some serious percussive sound design, Battery is perfect for me. Battery 3 is a little long in the tooth. There are a few things that doesn't make sense anymore so I am very excited about Battery 4.