Not one is the best security suite in my humble opinion. I've used the 'net for quite some years and the only one security software I've bought is a one-off payment for SAS.
No doubt others will disagree but for Vista and upwards Avast free AV is the bests. For XP then Microsoft Security Essentials is good.
For a blocker then Spywareblaster and/or Spybot S&D.
Malwarebytes and Superantispyware ,either one or the other, for a paid for version is good enough.
Be careful if someone suggests Hitman Pro as that not only cures trojans, etc, but will allow to clear so much you won't be able to use your OS.
Just my humble opinion only.