G DATA still have unresolved firewall bugs which has been reported over and over as well as many other things. Even G DATA themselves know of their performance issues in consumer versions, and the worst thing is nothing has been done since then. Also their other bonus modules which are included in IS/TS versions are not prioritized, so don't expect fixes. At this current time, Avast is better choice regardless of their privacy invasions.
If you care about privacy and security = G Data
Maybe it's a bit heavy
In my opinion, G Data is much better.
Avast still has trouble with the UI.
In terms of security and power, the suite is good, but G Data is much better than that.
For me the best protection is........ brain, the virus never comes by himself and one lightweight protection. I will not make my computer turtle to say I have the best antivirus with .... with ...... with ....
GData AV+Zonealarm Firewall Pro+Spyshelter Premium+OSArmor is the "combo" that im currently using.
Yes i've noticed some performance impact especially when doing software installations and file copying. But its not THAT bad.
But for sure, its heavy if using old and slow PC. For old n slow i recommend ESET or Emsisoft.