As stated above, go and handle/shoulder both guns. Some guns have different handle swells and forehand rests. Get a feel for which one fits you best. What may fit someone might not fit you. I recommend shouldering the different guns with your eyes closed. Once the gun is in place, open your eyes and see how it fits to you. If you need to adjust anything (head, shoulder, etc) to line up with the barrel, the guns doesn’t fit you. The gun should shoulder like an extension of your arm and fit without any adjustments.
Benellis are known for shooting higher then the point of aim. The beretta A400 has a big hand swell. Both guns are awesome.