I think you may be stumbling across a fundamental truth about dive lights: the constraints of engineering and technology make all of them fundamentally similar. All three companies have good records for execution, thus availability, price and even fashion become important factors.
I own a Sartek 10 watt and have been very happy with it, though I have had problems with the exposed switch and had to have them install a collar around it. I have used a number of different DiveRite lights over the years and have been happy with them, though I have had occasional problems with them flooding. My experience with Salvo is more limited, I've played with a 21 watt but haven't been wet with it yet - though I like what I see. Barry Miller certainly has a world-class reputation for designing and manufacturing lights.