I am presuming you have personal experience with Avast?
As when I looked at it up every site rated Kaspersky higher. Now im, not a big fan of just reading something and believing it hence I asked you.
Funny enough I use Kaspersky and I was looking for something that was lower CPU intensive, however, it seems (what they say) is that Kaspersky is lighter on your CPU.
I have never used avast to the extent that I've used Kaspersky so my opinion on which is better doesn't exist.
On the other hand, you might be looking at specific performance, rating type sites that specialize in this stuff? and not just what the google results say. IN that case, would be great full if you could share a link.