I've had less problems with my AEG then with the guys who use GBBR in the team.
Main recurring problems with GBBR comes from leaky mags so having an extra or 2 is good but costs more but fixing leaky mags is easy when you have the parts like said before me.
The only thing I find annoying safety-wise about GBBR is temperature fluctuations that affect them.
In the summer it's not all that different but a day that the temperature goes from low to high in a short period like it's happened, the GBBR may go out of FPS specs and you'll have to pass it through the chrony again and re-ajust it with your NPAS.
On the other hand, I've found them to be really easy to repair and/or upgrade compared to AEG gearboxes. For me, it's still easy but GBBR were less hassle.
For a new guy, buying an AEG first and upgrading later on to GBBR is the best option.
The only ones I recommend buying GBBR from the start is someone getting into the sport with veterans already using GBBR and bother buying the same ones as them first to get your experience done before trying to go for new ones.
We all end up getting something else at some point so there is no point in getting that exotic thing from the start. It just may crap your fun before you get into it because you end up not playing because of crappy performance and I say this because it's happened to 2 people in my team early on.
I've found that having both an AEG and GBBR is the best solution.
This said, it all boils down to one thing : GBBR really is more fun to use then AEG's and there is no denying that as this quote testifys :
Originally Posted by Brian McIlmoyle
Real life comparison,
GBBR- bang bang -- Giggle
AEG-- merrrzip merrzip -- meh