why about Real world system impact ?I vote for Emsisoft because
1. It has amazing Surf Protection.
2. Privacy wise it's the best Antivirus
3. It can block webaccess to harmful sites from any software. For example if I add my own list in Custom Host and try to ping it through CMD, Emsisoft will block that.
4. It has every hour update and auto-update for program works great ( unlike Qihoo).
Though I agree Qihoo is a great software.