Differences in opinions...what makes the world go round. Fortunately, the M14 came round, far surpassing the Thompson, the Mi and M3.
I always figured the Thompson and Grease gun, as short range weapons, rather than 'target' weapons per se, in any case..
I considered the M3 almost as a "last ditch" weapon, issued to mobile artillerymen, tankers or Jeep drivers..easy to stow away beside self, but still there..just in case.
I know the Thompson did well as a basic issue weapon for many troops in WW2, especially for the jungles of the
Pacific islands, and I don't doubt it's usefulness. It's just not my 'cup of tea"..