Plants grown under strictly MH with no HPS lighting will produce much stonier buds, but the yeild will suffer. Metal Halide lamps emit light containing UVrays HPS's dont emit light containg UV rays. Study after study has shown that UV rays increase the resin production in Marijuana plants. It would be ideal to have bothe MH and HPS lighting, but you can get yourself started nicely with the MH lamps. The buds wont be as tight and you wont yield as much as witha HPS, but the bud sure will be stonier if you know what your doing.

Plus any HID is better than CFL's.