It does seem that AV programme #1 will miss nasties that will show up on AV programme #2 and vice versa. Over the years I've seen several come and go from the top spot. I like KIS but better stuff is always on the way.
By the way, Kaspersky support is totally useless and the users' forum is excellent, http://forum.kaspersky.com/
I think KIS supports the forum if not its customers!
Forum experts advise that (1) you always update to the latest issue, currently 188.8.131.524 (2) don't overwrite your existing installation, remove it and clean-install the new one.