No matter what your standard, its better to know that any error is you, and not the grouping ability of the pellet, the gun, or any other factor, the cost of even the best pellets are the cheapest form of target shooting available. The difference in cost between the best and the cheapest pellets is
less than 40 pence over a full 60 shot plus sighters match course.

The difference are not just cost, which is minimal, consistency, and barrel fouling is also a factor, and then ultimately accuracy.

That's why I'd always advise to use RWS R10 in the weight and size for your gun.

Have Fun
Robin