Mossberg is cool but I'm a Remington man myself.I never fukked with it before. Except on COD. Honestly if you gone go shottys I say go for a mossberg
The ammo for 9mm is very affordable and the physical damage it causes to the body is comparable to the .40. Recoil isn't as bad so most people shoot more accurately with the 9mm, there is a reason Leo's and the federal government sticks with it.I would say start with a 9mm. Just my opinion.
Although I'm a huge fan of 45's
I'm not manly enough for the .45 though, that's a big round.