There seems to be a great deal of confusion regarding the WD Raptor 150 and the WD Raptor X. Are they identical internally?

The question popped up in a thread at the Storage Review forum. Both drives are supposed to be identical, but how do you explain the differences in test results?

Check out the results from Storage Review (note: Idle noise for the Raptor X is NOT 0db, it just hasn't been tested yet)

Raptor 150 vs Raptor X @Storage Review