I loved Bioshock so much that Bioshock 2 was an easy purchase. I personally loved Bioshock 2 more for three main reasons.
Firstly: I am a melee weapon kind of guy, and the drill was easy to use and killed very quickly.
Secondly:I loved the concept of Big Daddys and Little Sissters, so i found it very interesting to finally be a Big Daddy and play through their eyes.
Lastly: The point that tipped it over for me is the fact that you can have both your power and a gun out at once. It made Bioshock life much easier!