Symantec, McAfee and Trend Micro are the Big 3 in the Antivirus Industry. They have several products which deliver.
In my 10 years of computer experience, in which i sold more than 200 computers, installed more than 1000 Computers and trouble shooted countless computers, i always feel that what ever the antivirus it should have the Latest Definitions to provide effective protection.
So when you compare running the above against AVG Antivirus which is a Virus only scanner your system would be definitely slow. But you should also take into account the protection if offers.
My first choice would be Symantec Antivirus Corporate Edition 10 if you want a Virus and Spyware solution and Norton Internet Security if you want all in one solution. But remember Symantec, McAfee and Trend Micro charge for subscription to get the updates.
I have used AVG in some cases and would give a 5 Star rating for its abilities.
If you want to pay for your Antivirus go with Symantec or McAfee. Free would be definitely AVG. If your system is infected with Virus and won’t allow the existing Antivirus to run a scan and won’t allow installation of New Antivirus you can use McAfee Stinger.
It’s a single EXE file which would run and clean the Viruses. You can copy the EXE file to a boot CD and run the Application booting of the CD and running. This would allow the EXE to run and clean viruses without loading the Windows file system and hence effective cleaning.
Above link would allow you to download Stinger and has instructions on how to use it.
If you need any further clarification please get back to me.
For more blogs of Technology check my current blog at www.sunilsaripalli.com