..although McAfee and Norton do use more resources, almost all reputable lab tests indicate they are much better at scanning and cleaning viruses than the free programs such as AVG and Avast. McAfee and Norton, on most tests, score higher...although that depends on the test, the versions tested and the year of testing..If I remember, in 2003, AVG didn't pass the Virus Bulletin tests, but it does now..
Note that neither AVG nor AVAST were certified as to the ''Cleaning'' test at the bottom of the page.
ISCA Labs Certified List
Second, if you watch closely for sales in your area, you can find both Norton and McAfee for little or no cost...I happen to run McAfee exclusively (for a lot or reasons) and I've run multiple different versions. In the last 7 years, I've spend $4.95 TOTAL to use McAfee and keep it current. This doesn't mean that I'm trying to sell McAfee. I'm just saying, you can get most antivirus programs for not much money.
Third, Panda isn't free. At least I've never seen a FULL, free onboard version.Unless you're talking about their online scanner or their free trial software, their onboard antivirus, which is a good one, DOES cost money.
Panda Titanium Antivirus 2005
Next, if you check installation instructions for most antivirus program, they DO NOT advise installing two antivirus programs on the same machine. In fact, two programs running at the same time can frequently cause conflicts which make them both ineffective. I have read installation instructions to both Norton and McAfee and they advise uninstalling ALL previous antivirus programs, including their own, before installing the new version. I've had to fix computers that were infected simply because of this issue. If you check these forums, a number of users have problems accessing the internet, reading e-mail, etc. because two conflicting antivirus programs were running. In addition, even AVG 7 uninstalls the previous version of AVG 6 automatically before it installs itself..Unfortunately, there are a few instances where that automatic uninstall has failed and as such, most techs give instructions to manually uninstall BEFORE installing AVG 7. The ''old'' needs it gone so the ''new'' can work correctly. BitDefender 7.2 RECOMMENDS Uninstalling the Previous Version Also. The point being...two programs ''grabbing'' for e-mail or ''spooling'' a downloaded file will occasionally have problems.
Remember, I'm not saying two onboard AV's RUNNING at the same time won't work...I'm saying it frequently DOESN'T and is that really what you want from a security program?
ANOTHER IMPORTANT NOTE:
Because many of the newer viruses have the ability to disable the onboard antivirus programs, IF a virus get's on your machine, it has the potential to disable ALL of your antivirus programs.
Instead, I run online antivirus scanners to get ''second opinions'' regarding viruses...(Usually Trend Micro's Housecall or Panda) As you mentioned in your post above, they all have a different ''slant'' on the best way'' to detect and remove viruses. Temporarily disabling your "onboard" antivirus and running an online scanner shouldn't cause any problems.
When making a decision on which antivirus to install, choose wisely using all the available research, include your own personal preferences, and have fun shopping.
Hope this helps.