The answer: It depends.
If you've got the resources to machine one yourselves, there are many options on CD you may want to consider. Reasonably popular, if CD discussion is any indication, are
33's four-speed design, the
Nothing But Dewalts gearbox popularized by 47, and some older designs by
116,
45, and
716.
An evolution of 45's older designs became the AndyMark Shifter. The models available are similar in many respects; the differences are especially slight going from the original to the Gen2. The SuperShifter adds a few features; if they fit your needs better, great; if not, there's nothing wrong with saving the $30 a gearbox and sticking with a Gen2.
Last year, we used the Gen2 AM Shifters in our design, and I credit the ability to go fast and still push with a lot of our success. $330 a gearbox isn't cheap for a lot of teams (that's a lot of pizza for us!), but you get a bombproof gearbox that is ready to rumble--unbox, mount motors, put it on the robot. The time savings (particularly that time you'd spend machining) may make it worth the money even if you
do have the resources to make one yourself. However, that's a decision for your team and your team alone.