https://en.bitcoin.it/wiki/DifficultyPools "often do" pdiff, but it seems bdiff is what bitcoin actually does internally. Wouldn't that make bdiff the defacto standard? Since pdiff ends up slightly higher, there's no harm done. Anything hitting the pdiff target also meets the bdiff target. But isn't bdiff the true standard?
There's two different standards, but bdiff only makes sense in the context of Bitcoin because of its floating-point block target.
Pdiff makes more sense for pools, miners, and blockchain-independent difficulty measurements, especially since it can be easily compressed down to a single byte (by counting the number of zero bits).