Do .12 bbs work better with AEG guns?

Answer 1

No, they do not. .12g BB's usually have a lower quality than higher-priced BB's, leading to more seems and errors. They also usually have an air-bubble inside them, making them much more susceptible to shattering inside your gun, which would require you to strip and clean it.

You are better off with .20, .23 or .25g BB's.

Even a good quality .12 BB's (rare ocassions) is very easyly blown by the wind, so accuracy will be bad. For shooting long distances, better use .28, and for upgraded sniper rifles .43 is best choise.