Doesn't it really just depend on the level of consistency needed for the individual shooter's needs? An unregulated rifle will have higher velocity at the beginning of a complete fill, and will decrease in a nonlinear manner to a point, before flattening out, but continuing to fall off. If you are shooting a sufficiently large target, then the number of on-target shots may be perfectly acceptable, with distance being an important variable. If that is the case, then the added complication of a regulator might not be worthwhile. But, if the range is greater and/or the target smaller, then the greater number of shots at a smaller velocity variation will be beneficial.