6 Rem AI, 26" barrel, 95g Nosler s at 3500-3550 is real world accuracy node. In a 10T, 26" with zero freebore, I shot the 70g Nosler at 3950 into bug hole groups, and in a Shilen 14T, 26", off the same reamer, the 70's were at 4150 fps. The 70g Nosler ballistic tip is a deer bullet, make no mistake about it.
Std 6 Rem, 95g nosler at 3250 is real world, 60g Sierra at 4000 fps, both shooting tiny groups of less than 3/8".
6 Rem = 243 AI in capacity
6 creed = 22/250 AI in capacity, in fact if you stand them side by side, they are hard to tell apart until you look at the shoulder angle, as the edge of the shoulder height is darn near identical. So, the 6 creed would equal the 6-22/250 AI in capacity, almost.
You have to stomp the heck out of a 6 Creed to get the speed that the 243 AI does with little effort.
For shooting varmints, a .020 freebore 6x47 Lapua shoots the 70g at 3700 into bug holes, and the 6 XC does the same, I have both reamers.
For a speed demon with superb accuracy, both the 6 Rem AI and the 6/284 will get the job done. Since brass for both of these is difficult to get, a 6 Creed is an easy button and will get a tad bit more speed than the 6x47 and the 6 XC.
If dies were plentiful, I would be running a 6 SLR right now, which is a 243 that has been run through the 6 SLR Full-length sizer, pushing back the shoulder making a 30* shoulder angle, and ending up with a long neck. Good 243 brass is plentiful.
Folks are looking for something new and cool. I have had a number of custom 243 Winchesters with Hart barrels, every one of them shot 1/4-3/8" groups with 60-85g bullets for varmints. The 243 Win is famous with H1000 with the 105-108 class bullets extending barrel life with amazing accuracy. Old school 95g Partitions and 100g Hornady are Proven killers on hogs and deer in our family, and the New Berger 105g Hunting bullet is worth building a rifle around in how well it penetrates deer/hogs from all angles.
Great to have lots of choices.
PS. I am not a fan of short barrels unless it is the second or third chamber off of the barrel blank.