Top speed? You live somewhere you can regularly exceed 130 mph? If not, I don't see much relevance to that question, I have seen triple digits in our Supercharged RF before and after the supercharger was installed, the only difference is that I get there faster with the supercharger, I have not tested to see what our new top speed is today. None of our race tracks here in California have front straights long enough to push much beyond 115 to 120 MPH, car gets to that range and feels like it has more to offer but time to stand on the brakes and make the corner.
Have not found any differences here in engine reliability from supercharger or Turbo on ND Motors, the motor seems robust. But if you have motor warranty issue Mazda would obviously be in their right to deny coverage, and if that happens only Edelbrock has a warranty that would cover you. But given that it doesn't seem to really come up, I still don't see that issue as very relevant to choice of turbo or supercharger.
ND Transmissions are weak, adding boost won't help that weak box last. So far Mazda seems to be covering broken transmissions.
The Edelbrock Supercharger on my wife's RF has been no issue, and she is an ORIGINAL customer for that kit, she got it before it was available to the public, her install is oldest and she daily drives the car. Nothing has broken so far.