To each his own. I despise 777, I had to scrub my guns for what seemed like forever to get the crud-ring out, I go out to shoot and my time often limits how much I get to shoot With Blackhorn that's what I do.
On price, I have seen some of those ridiculous prices like at Bass Pro but have been able to get it at the same price as 777 or less by buying on sale and by the case over the Internet from Powder Valley.
You are pretty close to right on the velocity my own checking finds a slight advantage with Blackhorn when a tight sabot and enough wad pressure is use but at 110 gr and below there is not much difference; however I use up to 140 in one of my guns and I do find a big difference there.
I also find a difference in pressure the 120 gr load of777 shows the same pressure as a 135 gr load of Blackhorn with a 250 or 300 gr bullet and a bigger difference with a lighter bullet. If you did not know it Blackhorn is a progressive burning powder which means that with lighter bullets you have to put in enough powder to reach the efficient burning pressure before it becomes efficient and generates its full energy potential.
So what it boils down to is everybody needs to use what they like best, that's what keeps all of our suppliers in business and that helps the sport.