If you're going to build high velocity loads for 9mm, good load density is the best way to go. Extruded flake powders are often compressed in 9mm loads. Some ball powder loads will be as well. The advantage of using a ball powder, other than they will have much lower flash in many cases, is that with 100% load density with a dense ball powder you lessen the potential for bullet setback issues. Even though flake powder loads are compressed, they compress even more if setback were to occur.
I've used Blue Dot, myself. A lot of it, actually. In fact, one of the most accurate High velocity 9mm loads I've ever put together was with Blue Dot and a 115 gr. Winchester JHP. OACL was 1.142" and the powder charge was compressed. Kind of depends on the intended application, but AA#7 is a better powder to accomplish the same thing with very little flash from the muzzle. For 124 and 147 gr. JHPs, I don't think you'll find a better hi-performance powder. Another good one, if you want to pay more $ is V-V 3N37. If you don't care about muzzleblast, there is nothing wrong with using extruded flake powders like Unique, Herco, Power Pistol or Blue Dot. Blue Dot will obtain the highest velocity among them if you have the data, but I promise you, it will flash. Power Pistol flashes as much, if not more. This is based on actual experience and firing these loads at night. For light loads, use whatever you like for accuracy. But, what some people might not tell you is that high velocity 9mm loads can be extremely accurate and as capable of accuracy as lighter loads. The difference is recoil and the shooters ability to deal with it. Another Flake powder that works well in 9mm, but is single based, rather than double based like the Alliant powders is SR-4756.
Walkalong mentioned a very good and very overlooked powder for hi-performance loads in 9mm: WSF. I'm currently using something similar, but because many of my loads are defense oriented and get tested at night, I'm really liking Ramshot Silhouette. Very similar to WSF, but with a flash retardant. Silhouette was formerly sold as Winchester WAP and was one of the new generation powders, at the time, with WSL, WST, and WSF. Winchester was content to have only two powders that were dedicated to handgun loads: 231 and 296. 231 is the best selling handgun propellant in the US and 296 isn't far behind. Winchester dropped WAP and Western Powder Co. obtained the rights from Primex to sell it as Ramshot Silhouette. It is a very good choice for 9mm. the low flash aspect, high performance capability and by ball powder standards, it is lower in bulk density than the finer denser ball powders. Bulk density is 800 grams per liter for those of you who follow such things. What that means is that it will have high load density at a lower powder charge by comparison to the very dense ball powders. As far as I know, Winchester still loads a number of their faster autoloader cartridges with the Primex powder now known as Ramshot Silhouette. I'm pretty sure it was the powder used in their original .40 S&W loads as well.