I love both bioshock games, but even I will admit that the first one has a better story and is more intense. The second game is still fun, and it is great to get back into Rapture, but since you are playing as a big daddy, the individual splicers are less of a threat. The weapons are more unique, and all around more fun to play with, and you now dual wield a gun and your plasmids at the same time, but this mostly just serves to make it easier to kill the basic splicers. The other big daddies are tough, and the big sisters are a pain to deal with until you upgrade enough, so it can still be a challenge.
Also if you liked all the philosophy stuff in the first one then clap you'r hands together and squeal for joy because its back and there is even more of it this time around. More than anything else the game tells the story of Rapture not the character; when I am playing this game I feel like a side character in some epic tale, like it isn't my story at all. Rapture, the city and its history steal the spotlight, and that's not so bad in my book.
In the end my official suggestion is that you should play the game, but keep in mind that the story in both Bioshock games focuses on the city, and unraveling the mystery of what happened and what is going on; the plot is just an excuse to get you to explore new areas. This is more true for the second game than for the first one, but you should still keep it in mind, and if you aren't listening to every audio diary then you are cheating yourself.