I haven't had a chance to use a Kiev but I do love the Contax II. Mine has been super reliable for several years so I have not had to do anything at all but use it. For something that was built in the mid 30s that is amazing to me. Hook up the Sonnar 50/1.5, load some film, throw a meter in your pocket and go have fun.
I am clearing out my closets and selling off a lot of camera equipment but this, and my K1000, are two cameras that I can never see me selling.