We love it in Kalami but also like going into Kassiopi for a night or two if we feel like a boogie! Honestly if you are going with your boyfriend and you are like me and Andy you will love the tranquility and romance of Kalami.
Kassiopi is also lovely but I am biased to Kalami, as much as I love visiting Kassiopi by day and night, I would not stay there when I know the beautiful Kalami is only ten mins down the road!
They are both beautiful resorts and you can't go wrong with either of them.
Have a great holiday where ever you decide on.