Neither of the two is Metric, Whitworth or Pipe(triangle shape), the original is intended for self tapping plastic holes(softer), while the Chinese one is intended for metal sheet(harder), and hence the smaller pitch.
Yes, of course, it is better to not use the two screw types indistinctly, the Chinese one only on the hole that has lost its screw, but I think it is better to have one of these than nothing. On a "normal" use, the EP is opened very rarely. Like Zozo said, even the original screws will get loose after opening the machine dozen times. It is better, if the machine has to be opened frequently, to leave the screws not totally tight when closing it.
This is a good opportunity for keyboardjunkie(on the first commentary), who asked for 2 complete sets of screws.