gbb
pro:
looks/feels cool when shooting (more realistic)
short trigger pull
easy field strip down
upgradeable
con:
uses alot of gas
more parts to break
as soon as they get dirty they are just weights in the holster and when they do get dirty you have to tear the whole gun down to get it clean. (pick a good holster, cause it sux when you drop them in the sand.)
nbb
pro:
uses less gas
higher fps
internals dont get as dirty in desert enviroment
with a suppressor on them, they are dead quite
con:
full pull on the trigger every time
not many upgrades for them
hold less ammo
if i missed anything let me know and i can add it to the list.