The real answer is a pair that works best together.

In a round about way to answer-- I will NOT use AA powders. AA varies so much at times and has caused me major expenses and grief that I won't chance them ever again. Other than that you have to use whats best. You can have no favorite. You may love IMR but in a given gun the best powder may be Alliants RL. And then you have to pair the primer that the powder likes best. That can be from experience( IE I know that in my match rifles if I use Varget I'll be using CCI BR primers and that if I use VV N500 powders I'll be using CCI Mags or Rem Match) or purely from testing. Heck for practice stuff I'll buy surplus powder in bulk. And with those ball powders I used WW primers religiously as they were best till WW decided for some reason(stupidity) to make the cups thinner and more prone to pierce. Then I had to switch to Rem match.

So in reality if you have a handful of guns you can have no favorite single brand and expect the best performance.

Same goes with case brands. And with bullet choice. Choose bullets-- shooting highpower rifle I shot sierras because they were cheaper and accurate to beat all at 200, went to bergers for 300 because of the knots they shot there, and for 600-1000 I always use JLK for their accuracy AND performance.

Now if you are talking one specific caliber, type of chamber, brand of barrel for a specific use, maybe we could get closer to a consensus(not)

Jeff