For my team's applications, the AM Supershifter is the way to go. The gears are beefy, there are many gear ratios to choose from, and they fit nicely in our WCD design. For us, they have also been reliable. One of them is three hard seasons old and still works like it just came out of the box.
Also, having taken them apart for seasonal maintenance, the mechanism is robust and easily serviced with a hammer and basic tools
If you are looking at getting a set of transmissions for your team, define your goals while using them and make your decision that way. Each team is different and will prefer a different type of transmission for their typical drive train.