My experience is with both 133 and 8208....
..... and I have seen some pretty significant differences in group sizes with neck tension.
I have noticed that 133 likes more neck tension than the 8208 that I shoot (usually when the weather isn't so cold here in Michigan or I'm in a hotter/dryer climate, I would rather shoot 8208). My not-so-scientific thoughts on this is that it appears that 133 has a less steep pressure curve than the 8208/322/LT-32 type powders; which seem to build pressure faster. When you shoot 133, it has somewhat of a push kind of recoil. The 8208-type powders have more of a "pop" when they go off. (I said it was "non-scientific", but that is what I have seen.)
I've also seen that 133 seems to like to be shot farther into the rifling than 8208 does. In light conditions I have "jumped" the bullet as much as .020 more than where I normally shoot 133. I know that 8208, 322, and LT-32 aren't the same powder; and each has a specific sweet spot where they like to be shot. But, in my experience, these three types of powders shoot better in basically the same kind of temperature/humidity ranges, while 133 seems to shoot better in cooler/wetter weather than 8208.
I've used .262 neck exclusively since 1996. Looking back, I would have liked to go thicker, especially when using 133, but that has ended up being what my system that has evolved; and I haven't committed to gong to the thicker necks - which would require a new reamer, seating die and bushing set. Not to mention, I would have to go through a new tuning regimen to see what changes with the environmental conditions. (Or maybe I'm just lazy.) Today, I cut necks to .0081 so that the loaded round comes out below .261, closer to .260. I use a .256 bushing for 133 and a .257 or .258 bushing for 8208. With the .258 bushing, you can almost pull the bullet out with your fingers alone. I have even shot light-tensioned 8208 loads with bullet seated out past the "jam" and allowed the rifling to seat the bullet.
The guys shooting the thicker .265 to .268 necks and astronomical amounts of 133 have had great success in all kinds of weather conditions. But, I can't get 30.5 grains into may cases and still have the bullet hold the same seating depth (the powder pushes the bullet back out with compressed loads). This is mostly because when I have cut the case necks as thin with my chamber dimensions, there isn't enough "meat" in the case necks as the .268 guys have to hold the bullet in with the compressed load. (Another aside, I have noticed that with shooting over 30 grains of 133 in a standard-sized PPC case, the powder seems to burn "cleaner" and there is less powder residue in the barrels; another reason I would have liked to go thicker on the case necks. Oh well.)
At have for years tuned my rifles at 200 yards because the differences seem to be more easily seen on the target than at 100. When I've shot the tighter "grip" with 133, it was quite easily seen in the repetitive group size; more threes than fives. The same with 8208 or 322 with the more loose neck tension. In fact, I have also seen that 133 shoots better with newer cases than the 8208 does. I will often shoot brass with 133 until it gets more worn, then I will shoot 8208 in those cases.
The one other thing that had become very easily seen in the 200-yard sessions is that groups will open up if one doesn't trim the cartridge length often. (At the Nationals I would trim cases after each firing.)
I guess when you have a boring life and spend a lot of time at the range (especially at 200 yards) trying minute changes in tuning variables, certain patterns start to emerge.
