Just wanted to add that which ever one you choose I would definetly go with the cantilever mounting system. It is much better to have the scope mounted to the barrel than to the receiver on a shot gun or any "rifle" that has an interchangeable barrel
Why is it better to have a cantilever mount on the barrel? I would argue the opposite, if the mount is on the barrel and you switch the barrel out you will lose the mount. My Mossy 500 is drilled and tapped and I have no problems. My 870 has a cantilever mount and every year takes a little tuning to get it back into form. My cantilever mount is off of the receiver though... Are shotguns that much different than ML or rifles? They of course are drilled and tapped?