Hello JB007,
I voted for ESET, because it should be easier and faster to your system with its Single-Engine. G Data is much heavier at taking system performance.
ESET's reaction time to new malware is also one of the best. ESET and Kaspersky are one of the first, which have new definition files for new ransomware/trojans all the time. BitDefender is much slower there - so I guess, G Data will be slow there, too.
G Data only got the advantage that it's using a dual-engine for scanning, but you could compensate it by using Emsisoft Emergency Kit and Zemana AntiMalware Portable for regular scanning of your system.
So the facts: With G Data, EEK and Zemana you only have three engines and three virus definition databases. (BitDefender, Emsisoft PUP/PUA and Zemana)
By using ESET you have four engines and four virus definition databases (ESET, BitDefender, Emsisoft PUP/PUA and Zemana) - so you should reach a higher detection level with ESET and that second opinion scanners.