Conversion Bulbs

Has anyone used conversion bulbs and if so, did you think it made a differance ?
I have 27 plants under 2 400 watt MH's and was thinking either get one sodium to add to the 400's or conversion bulbs.

i have one 400w hps with a mh conversion bulb. the mh really made a difference in my plants, in veg. they were more bushy. and grew faster. As far as you switching to to the hps, im sure you could expect bigger buds and more crystals. I have never fllowered with mh so i cant tell you exactly how much more of a benefit it truly is.