Key thing to remember is that AVs perform differently on different PCs. What may work great on my system may be a disaster on yours. So why don't you try them both to see which works best for you, on your system. Qihoo is free, wouldn't cost anything but time to check it out. I've never use Kaspersky, but if they are like most paid AVs they probably offer a trial period where you check it to see if it's worth paying for, for your needs.