Paid firewalls vs. free firewalls

I've tried a few free firewalls after my free trial of Firewall Protection program expired, and decided, before commiting myself to buying one, to try out some free ones. Unfortunately, these didn't perform quite as well as my original Firewall Protection did. Spyware and adware seemed to slip right through, even though the products claimed they wouldn't. That never happened with Firewall Protection. Finally I decided to remove all free firewalls I tried, ante up, and pay for Firewall Protection - I didn't mind, as I easily could have paid twice as much for the supreme protection it offered. To this day my computer is still spyware, adware, and virus-free.