In terms of detection rate
Panda free antivirus 2015 is on par with Kaspersky, Eset internet security softwares. The thing you lacks on Panda free AV is the firewall. But windows firewall is pretty strong and competitive to paid internet security softwares.
So why you need to pay for security softwares when you can get similar level of security and performance on a free solution with usage of
Panda Free antivirus + Windows firewall ??
Here I am listing the AV-Comparatives Firewall test report of 2014, reviewing the ESET Smart Security 7.0, Kaspersky Internet Security 2014 and the Free Windows 7 Firewall performance.