The Marvel conversion is the one favoured by American bullseye shooters for accuracy (great) and reliability (better than the others but still finicky). An NRA 2700 bullseye competition consists of a 900 with .22, 900 with a centrefire pistol and a 900 with only .45ACP. Most shoot the last 1800 with their .45's so as not to have to use three different guns, and many of those use the Marvel conversion unit so that they shoot the full 2700 with the same gun. They know what they need to shoot well and to shoot without malfunctions, and they virtually all choose the Marvel unit.
Having said that, they are expensive and you probably aren't going to shoot NRA bullseye competition.