There are several reputable labs which test the effectiveness of major anti-virus programs and security suites to include AV-Comparatives.org, Virus Bulletin Comparative Tests, AV-Test.org, NSS Labs Consumer Anti-Malware Products Group Test Report, etc.
These kinds of comparative testing results will vary
depending on a variety of factors to include but not limited to who conducted the testing, what they were testing for (type of threats, attack vectors, exploits), what versions of anti-virus software was tested, what type of scanning engine was used, and the ability to clean or repair. There are no universally predefined set of standards or criteria for testing
which means each test will yield different results. As such, you need to look for detailed information about how the tests were conducted, the procedures used, objectivity and data results. Read Anti-Malware Testing Standards Organization: AMTSO Fundamental Principles of Testing
Each security vendor uses their own testing/analysis methodology to identify various types of malware so the detection results are not always the same.
Some of the testing criteria and standards may even be misleading.
Comparative testing: A bit of background for the uninitiated
...for some unknown reason...the renowned German test lab AV-TEST has quietly (there was no warning) modified its certification process. The changes mean that the certificates produced by the new rules are, to put it mildly, pretty useless for evaluating the merits of different AV products...With AV-TEST’s new certification standards, the onus is on the user to carefully investigate the actual results of each individual test…they may find that a product that blocked 99.9% of attacks has the same “certification” as a product that only blocked 55%.
(Symantec) is as good as any other well known anti-virus program, it is costly, requires numerous services and running processes that consume system resources and often results in complaints of high CPU usage. Anti-virus software components insert themselves deep into the operating systems core where they install kernel mode drivers
that load at boot-up and create files/folders/registry entries in various locations.
I have read from other users that Norton has made improvements in newer versions of their software so they are not as resource heavy as past versions...while others still say differently. Those issues plus the cost factor are the primary reason many folks look for a free alternative. IMO, Norton is better utilized in an Enterprise system environment
protecting many client computers. With that said, there are a lot of folks who prefer using Norton (especially if it came preinstalled) and there is nothing wrong with staying with a product you are satisfied with.
Most Internet Security products include antivirus and firewall protection plus various other features depending on the software vendor...and for those reasons it is called a Security suite
I'm not an advocate of suites. All-in-one tools and suites are filled with extra features (including "bells & whistles") which typically use more system resources than separate programs that do the same task while other suites leave a much smaller footprint. Suites tend to have varying degrees of strengths and weaknesses accorded for each feature they incorporate. Internet Security Suites include a Firewall component, which IMO is unnecessary since the Windows built-in firewall is adequate protection
and many folks also use a router. In contrast, separate tools are designed, built and maintained with a greater focus in a specific area so they are generally of better quality and more effective at what they are designed to do. This means the program's performance for that particular feature is usually superior than their all-in-one counterpart. Further, all-in-one tools generally do not allow the user as much flexibility in tailoring program settings and usage.
If you are adamant about using a suite, then I would recommend one of the following: