I have had all three at one time or another.
The very best agg I have ever shot was with a 30BR, a National Records Committee measurement of .154. That is about as "official" as you can get.
I still rely on the 6PPC for the vast majority of my Group Shooting. The 30BR is a HV, which limits it's participation.
For score, a "sub .200 agging" 30BR will beat the pants off of a "sub .200 agging" 6mm. But, the big catch here is both Rifles have to be tuned into that capability. A mediocre 30 is just that, mediocre.
Mike Stinnett of Oklahoma shoots his version of a 30 based on the Gredal Case, it is in reality a "30 PPC long". He does very well with it in both Group and Score.
In my opinion, while the 30 is just as accurate as anything, (by that, I mean it's ability to shoot sub .200 groups on a consistant basis), you have to really love it to want to put up with the extra recoil, and even cost, to justify shooting one in Group.
If it wasn't for the Sporter Class, I suspect you would see a multitude more 22 calibers. A 22 PPC Short just might out agg them all.