I bet even with the 30 day free trial that comes with KIS he would still choose CIS becasue.... as dieselman said... it's free.
If you stack CIS and KIS side by side... completely ignoring the price tag on KIS
You'd notice that CIS bugs you for just about everything you do on your computer where as KIS does it automatically.
Sometimes with Defense+ I feel like I'm hitting "Allow" just to open the start menu. >.>