ThunderCactus is also a tolerance nut. When he puts a gun together, it isn't like your average gun doctor putting a gun together. He'll get the absolute most out of his guns, and regularly maintain them to keep the high tolerances and consistencies. I've been impressed with a lot of his weapons, most notably his SAW, and VSR; his M249 Para was a terror, and his VSR didn't like to miss it's mark.
I find a real beast of a gas gun is truly more expensive than an AEG though. But an argument can be made for both. To fully trick out a GBBR with RA-Tech may cost over $1000 on top of the stock gun; and then if course there is the ridiculous magazines. An AEG is usually cheaper stock, but after dumping in revolution kits, mosfets, etc you can spend over $1000 as well. In my opinion an AEG is cheaper on replacement parts and fixes.
If you want true performance then I've been more impressed by GBBRs minus ones with severe temperature variations. A heavy temperature or FPS change can throw out your shot a little. You may have to re-adjust your hop-up or change BB weights to compensate.
The short answer is GBBRs are exciting, AEGs are ....not usually, but if your going to spend the cash for high end buy a Systema or a Fight Club Custom.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē