styles

Im in the market for a new shotgun and ive narrowed it down to these two but now im stumped. Ive never owned a semi auto sg before, only pumps. Which one of these two would be more reliable with cheap target loads? I wouldnt shoot that all the time but when i did i would want the gun to function properly. Its my understanding that the inertia system was benellis claim to fame and the m4 if thes only gas gun they make. So which of these systems is considered the best? I can only buy one and i want to get it right the first time. What are the pros and cons of each? Ive already read alot but i figured the best place to get honest info on benelli shotguns would be the benelli forums. Thanks guys.