Too many variables.
Do you reload or will you be using mostly factory ammo? Are you looking for something to hunt with that can share ammo with a pistol at the range? Are you looking for something more tactical? Does it matter if its magazine fed? Do those magazines have to be shareable with each firearm? Are you looking to modify either of them? What range are you looking for, what power, what kidn of optics would you want to mount etc etc etc...
Just pick whatever you would choose and have fun with it.