I also use F-Secure which is about to expire, so I tried Avira to trial it and uninstalled it after an hour as it refused to let me connect to the internet, I suspect firewall issues were to blame but couldn't sort it out. I tried KIS last year and the firewall drove me nutts!
F-Secure I find is user friendly, I've had no real problem with the firewall at all, and I'm used to its ways. To be honest I would like to try something different myself but it might come down to "better the devil you know" I've 16 days to make my mind up lol.
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