By itself, a vacuum pump is only good for about 14 inches (Max) if they're cranked up . . And there's a lotta wear n tear on em when you're asking that much from one . . Prices on them are around $850 new and while they do pretty good, I'd always choose the dry sump even though it's a hell of a lot more expensive . . By itself, a good 3 stage pump will give you 18-20 inches of Vacuum, which should be the equivalent of a new set of heads with shaft rockers in the HP department . .
Over the years, though, I never thought of a dry Sump system as a HP advantage, but in drag racing, more of a engine safety program . . The system takes inertia out of the ballgame, so to speak, because when you do a hard burnout, you stand the back tires up, pitch the front end down, and then brake hard at the end . . where's the oil in the pan? The front, mostly, away from the pickup, if you have a conventional system. And when you leave, anything quicker than a 1.40 60 ft time, and all the oil is piled up in the back of the pan and up around the rear main. At the other end, when you are getting stopped, where's the oil, again?
With a Dry Sump, your oil pressure never wobbles . . Because it's less subject to movement and inertia . .
But, there's budget, and there's what each individual may see as a solution for his own particular situation . . Whatever works for you ain't bad even if other guys scratch their heads . . . And if they ask, I always say, "Becuz, I didn't know no better!"
Never apologize for what works for you . . .