Look at the "block counts" rather than the file counts.

Oooh, good spot. Probably part of the problem is that the slow drive was mke2fs'd with a 1K block size, and the fast drive with a 4K block size. With nearly half the files on the filesystem several megabytes in length, 4K is obviously more efficient. The slow drive is only 30% bigger but has five times as many blocks, and I can bet fsck has some data structures sized by block count. Were these drives formatted with the builder image, or by hand?

Peter