Nobody has asked you what you shoot well, or what you like.
That is, to say the least, a consideration.
The chances of you meeting 30 bad guys at once is remote; the chance of you surviving such an encounter is negligible.
You may extrapolate the scenario as required...and make your decisions accordingly. There is no such thing as too much ammo, but on the other hand...there is no reason to carry 100 rounds into battle against six (or 16) aggressors. If you are Bruce Willis, you will prevail. But reality is not a movie.
So...make your decisions based on reality. It becomes less a matter of what holds mega rounds, as what you can shoot well in extremis.