i didn't know who to choose!!

Neither do I!!! ^

Neither do I, I guess Katherine because she's older than Damon?

I don't know, I feel like Damon's humanity might give him an edge...that sounds weird, but I feel like if he REALLY wanted to save someone like Elena, or Stefan, his humanity and love, which would lead to SEVERE DETERMINATION would give him the edge.

She's ten times older, therefore she's ten times stronger.

As much as I hate to say it, she could kick his ass...

Katherine has something over him... He wouldn't like to kill her so he will skip, Katherine would kill him EASY!

A.Katherine is way too stronger than Damon.
B.She's kind of cold-heart bitch (but I like her xD) and she would kill Damon without second thought.
Hope this will never ever happen, though..

She's older, and therefore stronger. Furthermore, Damon still has feelings for her, while she cares little about his life, if he were to die, she wouldn't care very much. On the other hand if Katherine was in a life-threatening position Damon would save her. Of course Katherine would win. She's Katherine! <3