Out Of these two kaspersky internet security hands down everytime. Kaspersky consistently performs great, they do a lot of research. This is just my opinion but at the moment Avast isn't even in the same league as Kaspersky.
There is no point in paying for Avast. You get everything you need with the free version. With that being said, definitely KIS. It offers a level of protection that surpasses Avast and to be honest most other AVs. I would say it is in the top 2 best in the industry. Download it for yourself and try it out for 30 days. Also check out the Malware Hub and Video Reviews to see how it performs.
It depends! If you're a top-notch user then go for Kaspersky on manual mode and you'll get superior protection ( I mean if you can well deal with warnings requiring advanced user to decide). But if you're an ordinary user just go for Avast. It offers excellent protection and simplicity. Also Avast is lighter than Kasper is. ( on my sister's laptop Dell Inspiron N4030)