I like
Christine best, partly because I have a loathing of the nn
Tina, which is more likely to come out of
Christina and
Kristina.
I also know a horrible
Christina, who has tainted the name pretty thoroughly. I like
Cristina though.
Kristina looks misspelled to me, even though I know it's not, because I'm used to lots of C names being changed to Ks.