While a knowledgable person can make an Edelbrock work as good as a Holley, my impression has always been that it takes a smaller parts inventory to make a Holley work for competition . . Holley's are a little simpler in their operation, so for the "Physics Impaired" (myself included) they were my racing preference.
Currently we're using a SV-1 and it's almost "Magic"! Altitude doesn't seem to have much affect on it, at least we haven't noticed any changes in plug color and the A/F meter says everything's right on the nuts . .
On the other hand, on my Street Rod, I used an Edelbrock 650 on top of my 144S Blower/330 Vortec and it worked pretty darned good. We changed the high speed 4 steps leaner and it worked great . .
Currently I'm using a 2" throttle body on top of the blower and a '91 GMC HP chip and it does even better . . Smooth, dependable and gets decent mileage . . And still gets on the tire when you mash yer motor . .