I used to flower under HPS exclusively, but now i veg under a cool 400MH and switch to a Warm Deluxe MH for flower. Like Dutch said, mine stay a little shorter under the MH, but with the naked eye resin production appears better. Also didn't lose any notable weight at harvest.

Plus I like the full spectrum of light for diagnosing problems, much easier for me to see problems without having to move my plants out of the grow space.