Gdata uses Avast's engine, infact it uses two, Bit Defender and Avast the last time I checked a couple months ago. Norton Security tools for home users is pure 'Grade-A' crapware. Fanbois are usually the ones recommending the software and are usually only using it because they got caught by their marketing schemes. That is, buying a prebuilt machine from a large retail outlet like Staples/Wal-Mart/Futureshop/BestBuy etc..., and having Norton Internet Security preinstalled. Then when Norton Internet Security starts to state, or I should say scare the user, that their system is not going to be protected any more and open to all kinds of threats. This is when the user should uninstall it and go with another solution. I have a friend that won't change his Norton Internet Security because he paid for it and doesn't want to waste a years license but he just can't grasp the concept of how bad this route is. Loose the subscription people, and I HIGHLY recommend using Avast Internet Security or Avast 7 Pro if you can afford it. If not the free version is absolutely fantastic and feature rich, more features than full flagship solutions a few years ago from similar developers.
Just always make sure you understand that no one security solution is best or will protect your system from every threat out there. I run Avast Internet Security with realtime scanning enabled and also run a couple malware scanners every other week. Avast doesn't really scan for tracking cookies for example but a program like Malware Bytes/SuperAntiSpyware/Exterminate IT! or others like CCleaner/Cleansweep/HiJackThis. If your also wanting to cleanup your system and check for various errors automatically with heaps of excellent tools is Tuneup Utilities 2013. Tuneup Utilities 2013, Total Uninstall Pro (the best snapshot uninstaller PERIOD) and Avast Internet Security are always installed on my machines, right after a format as well.