I've tried a lot in my experience. I have the following conclusions for myself:
1. Never use Norton AntiVirus, because it will slow down your system terribly
- Norton is very suck.. it takes a lot of memory
2. Nod32 is very weak, if not incapable, in catching spyware/adware, but it advertises it
- never use this Antivirus
3. F-Prot is very friendly antivirus program and one of my favourites, but it catches viruses only - no spyware/adware
- i didnt notice this is Antivirus.. its freeware version or shareware version??
4. Avast is average quality
- avast more bout skin and interface.. not good enought for Antivirus
5. AVG is more than very good, but I don't like the interface
- im satisfied too.. its faster but the virus definition was expired quickly
6. Kaspersky, like NAV, is taking a lot of resources
- not working with that..
7. Trend Micro is average too
- i never used it