[Oni]

This is a pointless comparison:

1. They are made by the same developers of BT, Offensive Security.
2. Kali is the complete OS of BT, meaning you actually install it, whereas BT was designed for Live CD booting, with the option of installing permanently.
3. Kali has larger database of features and applications.

Not exactly. There's a few characteristics that might cause people to prefer one over the other. As I mentioned, one of those characteristics would be the distribution they are based off of. Kali is based on Debian, while Backtrack is based on Ubuntu. I know a few people that are still using Backtrack, even though I suggested Kali. People have their reasons, I guess.