GBBR are not for noobs ... It's not something easy anyone can use, it needs a lot of care , especially the mags. If you are tight on budget, do NOT think about GBBR. Each mags are like 40-50$ (good ones) ... Though, upgrades seems to be easier
and also, GBBR gives players more realism because of the blow back effect which is indeed awsome. Accessories and attachements are the same.