I only have a little experience with the Thompson SMG in this respect, and only in peacetime.
I thought that the drums were great when impressing friends with full auto fire demonstrations, but in every other situation Ifound that I preferred the 30 round "Stick" magazines. It drums were noticeably heavier, slow to load and made the weapon clumsy to handle. The clumsiness was probably the deciding factor for me.
"I am totally responsible for what I write,... however I cannot be held responsible for your complete inability to understand"