Personally I always liked W231 in 9mm loads.
Here's a couple of things to keep in mind no matter what powder you decide to use.
There's a lot of variation in 9mm brass, so if you work toward max loads this is something to be concerned about if you are using mixed brass.
The other is Berry's bullets, years back I bought some Berry's bullets to load 45 acp pin loads.
The bullets were great looking bullets but I noticed some of my pin loads showing pressure signs.
It was not a mixed brass issue as I was using all Starline brass from the same lot.
It was not a powder issue because each powder charge was hand dropped and I would check the measure every 10th round, the measure setting never moved.
So I started checking bullet diameter, there laid the problem. Some of the bullets were measuring as high as .458 in diameter. So I measured all the bullets, used only those that measured no larger then .452 and gave the larger diameter bullets to a friend that had a 45 revolver with a generous bore and cylinder diameter.
I could only use about half the Berry's bullets I purchased so I never bought anymore.