I do believe the Phantom Special is ground THICKER at the bottom, not thinner at the bottom like MK Dance. I'm not sure about the Gold Star. (Of course, the side honing isn't done up the whole height of the runner - just the bottom portion that might be used to skate. I think they take a swipe on each side with some sort of cutting or grinding tool, centered something like .1 - .2 inches above the bottom.)
Incidentally, a skating manual from about 1920 talked about parabolic, tapered and vertically side honed blades too - and didn't come to any conclusions about whether there was a benefit. People have been arguing about these things for at least that long.
One thing that is clear - if a skate blade has any type of side honing that affects the bottom of the blade, it becomes a lot harder to sharpen well. Unless your sharpening pro is very, very good, it doesn't make sense to try blades with any type of side honing that affects the bottom of the blade.
And as far as the structural forms of side honing that don't affect the bottom of the blade, which shave off a few grams of weight, the Ultima Lite blades, in which the less important parts of the blade from a structural perspective are completely cut away, are probably even lighter.
The best sharpening pros around here say that it is good business practice to give customers whatever they want. If a customer requests side honed blades, that's what the customer gets.