I loved Ziva immediately as a character, so I thought I wouldn't like Kate at all (actually, I think I was almost determined NOT to like her) but after watching the entire 2nd season, I decided she's a great character - but I still like Ziva better. Ziva and Tony put themselves on equal footing, and although there's tons of teasing between them, I think there's also alot of equal respect there for eachother too, IMO. With Kate/Tony, I got the impression that Kate didn't have as much respect for him - until she almost lost him in "SWAK", then she realized how much she cared for him. Plus I really like the McGee character, and Kate always joined Tony in badgering him in S2, and definitely didn't show much respect for him (although I do realize the "probie" will get the butt of the teasing). Once again, just my opinion, but I think Ziva has a much greater underlying respect for McGee as both a person and as a fledgling agent, and it shows. Her teasing of him is more tempered and good natured, and less condescending.