Security suites have a firewall, plus antivirus and antispyware programs, and often spam and popup blockers. They could be substituted at Step 1, 3 and 4 of the "Rudimentary Defense" plan.
Their various components will be less likely to conflict with each other than the elements of a defense suite made up of "best-of-breed" components.
They cost less in the aggregate, and they are easier to install, understand, use, update and manage than an equivalent random collection. In short, they can simplify your life.
There is less overlap of functions, e.g., antispyware and antivirus, and that reduces competition for computing resources. That means they will not slow down your computer as much as a full array of defense software will.
Security suites could have one vulnerable point -- an Achilles heel -- that will let malware kill all the defense measures in one blow. There goes your layered defense. That's their biggest negative.
It's tough for each component in a security suite to be best-of-breed. A system assembled from the best individual firewall, anti-spyware, antivirus, and intrusion prevention solutions can provide better defense.
If you decide that a security suite suits your security needs, the next question is, "which one?" I don't have much personal experience with security suites. When I run across good reviews of security software I add them to my Security Software notebook -- the latest ones are at the top of each category.
Home PC Firewall Guide has an extensive index of comparative security suites reviews. Windows Secrets has a list of primary review sources. You'll find an extensive report at Tech Support on how hard it is to pick the best suite. You can always consult these and make up your own mind. :-)
Getting to know you:
A full security suite will pester you with many questions and alerts when you first start using it. It's important to deal with them as they occur. They'll slow down over time.
Be cautious when the alert is directly related to a website visit, or while you're accessing an email message or attachment you'll need to evaluate it carefully. If the alert appears in direct response to some action you intended, like installing a known-good program, you can be more confident about allowing it.
If in doubt, let the security program block the action. Then try what you were doing again, and watch what happens. Maybe you'll learn enough to be confident about allowing the action.