One of my friends uses Bullguard. When he first installed it he loved it and tried to convince me to switch. Lately he has been having problems with updates and support; I think it was reduced frequency of updates and poor support (difficulty in obtaining a response, and lack of knowledge when a response was obtained). I personally know of no one else who has tried Bullguard.
I have had no such problems with Avast, on my daughter's computer and on my mother's (avast home) nearly a year, and on mine (avast Pro because I sometimes work at home) since February. I replaced paid Norton Antivirus and Norton Internet Security on all of them, with 10 months remaining on mine.
Avast! support is excellent!
Terry
P.S. If you are using Bullguard Internet Security and switch to Avast, you will also need a firewall; there are some good free firewalls available.