I believe that a gun has to fit you properly to be effective. I personally own a Xtrema 2 and before that the AL391 I found that the Xtrema actually fit me better.The position of the grip was different enough to make it fit me. The main differences between the Xtrema and the Vinci is that the Xtrema is gas operated and the Vinci is inertia driven. The Xtrema 2 can shoot 3.5" shells the Vinci cannot. Not a big deal especially with the great selection of 3" ammo available. The Vinci is a pretty light gun as well 6.9lbs which maybe a handful with big magnum rounds (ie: 2oz turkey loads), the Xtrema is approx 8lbs. As for reliability I believe that you won't go wrong with either gun. The Vinci is a cool looking gun, but I would handle both before I did anything. I would also look at the Beretta AL391 as well because it is a 3" gun which would be comparable to the Vinci. The prices I found were as follows Xtream 2 w/KO is $1865, without KO $1600. AL391 $1360 or w/KO $1720 and the Winchester SX3 is $1350. Couldn't find a price for the Vinci but I guess $1600+.
Good luck on your selection. Scott