G DATA provides some of the best Android virus protection on the market, according to AV-Test and AV-Comparatives. However, expect to pay for the full version as most features are locked out to free users.
30 day premium trial
G DATA's light version wants to convert you to a paid user. You'll be missing a lot of features if you don't upgrade. However, you do get a pretty lengthy 30 day trial to see if the app is something that's worth it to you.
Premium features include SMS commands to help you find, lock, and track your phone if it's lost or stolen. This is a unique implementation of anti-theft since Google's Android Device Manager requires an active internet connection to work. SMS has a greater chance of reaching your phone.
There are also parental controls in the form of Children's and Teenager's corners, which locks access to parts of the phone. This is a nice addition since Android's parental controls are still lacking.
G DATA has a frustrating interface. Everything is buried behind its side menu so you'll be jumping back and forth to that menu to do anything. It gets annoying but thankfully, the app is designed to stay out of your way most of the time.
G DATA has great detection results and its scans are quick since the interface is so stripped down. Free users are limited to on-demand scans.
Barebones free antivirus
If you're looking for fast on-demand scanning and some anti-theft features, ESET is great. If you're expecting more features for free, you're going to be disappointed. There are free antivirus apps that include more features, like McAfee and Sophos.
Great for subscribers, not great for free users
G DATA doesn't give free users much, just on-demand scanning. That works if you think your phone may be infected already but it doesn't do much to protect you. If you don't want to pay for an antivirus, there are better alternatives, like CM Security.