As in all things on a boat, selection and location of a wind generator involves compromise and as responses to your inquiry reflect, opinions will vary considerably. Here are some thoughts:
1) You need to check amp output of the various generators at various wind speeds and determine what will be the most likely average wind speed you will encounter during your voyage. The D400 turns at very low wind speed but maximum output is lower than others. As you increase maximum output, you reduce output at lower wind speeds.
2) Noise and vibration are a consideration. Check user comments on the noise factor of the various units. You don't want to be that vessel in the anchorage that every tries to get far away from because your generator is making so much noise. Most generators produce some vibration (apparently not the Superwind according to Danny). Sometimes the vibration can be dampened, other times it's not bad enough to keep you awake at night. Some of this can be mitigated by where/how it's mounted.
3) Top of the mast, middle of the mast or stern arch? Keep in mind that the generator output is not same as the amount of charge that reaches your batteries. The further the generator is from your batteries, the lower the charge is that reaches them. As has been mentioned, maintenance can be an issue if mounted at the top of the mast. How to deploy the ballooner can be an issue if mounted 1/2 way up. Vibration can be an issue on the stern arch.
4) Cost. As Danny eluded to, the Superwind is top of the line, so it had better do everything well. If cost is no object, that might be the way to go but if you have a budget, perhaps you can live with a less expensive option and mitigate any of it's shortcomings.
We installed an AirBreeze with aftermarket blades (which significantly reduced the noise and vibration) at mid-mizzen mast. We could not hear or feel the generator in the cockpit. In the aft berth, we could hear a vibration hum but it was not unpleasant and its intensity would alert us to increasing wind speed at night. Each time we'd leave the boat for the off-season, I'd remove the blades, eliminating any concern for excessive wind -much easier to do than at the top of the mast. We'd activate the generator brake whenever we'd raise the ballooner and turn it back on when the sail was deployed. We circled the earth with this set up for 7 years and have no buyers remorse. It was half the cost of the Superwind.