Looking at the 10 products which received perfect 13.0 scores from AV-TEST (Avira, Bitdefender, G Data, Kingsoft, KSMobile Clean Master and CM Security, KSMobile, McAfee, Qihoo, Trend Micro, and TrustGo) and counting features from the feature chart, the best feature sets appear to be from G Data, McAfee and Trend Micro.
G Data Internet Security costs $20.75 and does not appear to have a free option. Google Play says there are 1,000 to 5,000 installs and 143 user reviews give it a 4.0 out of 5. For some reason, Play says it is incompatible with both my Google/Asus Nexus 7 (running KitKat) and my AT&T Samsung Galaxy S4 (running Jelly Bean 4.3).
McAfee Antivirus and Security can be downloaded and installed for free. The premium version costs $29.99 for three devices for one year. Google Play says there are 5 to 10 million installs and 47,729 reviews give it a 4.2 out of 5.
Trend Micro Mobile Security and Antivirus also has a free option. The premium version costs $29.99 and the site says nothing about whether the license covers just one device or more. Google Play says there are 1 to 5 million installs and 17,484 reviews give it a 4.5 out of 5.
From what I see, there's no clear winner here and there are too many variables for a third party like me to tell you that one product is best. But the AV-TEST results and other information on Google Play should give you all you need to make a decision for yourself.