For semi-autos (assault weapons for any liberals reading
) #1 is stock fit and balance but #2 is a reliable cycling system. To that end there are benelli's (no gas) and berettas (gas) and A5 type actions (NLA IIRC). EVERYBODY else (barring those who use the benelli recoil action system) is just making excuses.
One other important factor for those that actually use their semi-autos is ease of cleaning and frequency required. The two B's win again.