HPS question

On the lights that are mh/hps both is it worth it to spend the extra money ? do Mh and HPS have different threads at the bottom of the bulb or will they both fit into one socket and the ballast is just diff ?

ex. will this light have one socket with a special ballast to run both bulbs? http://cgi.ebay.com/DIGITAL-600-wat...42225QQcmdZViewItemQQ_trksidZp1742.m153.l1262

and will this be too hot for a closet with JUST oscolating fans ? (6Lx4wx8h)

If you are setting up a grow closet and only want to have one light than a mh/hps ballast would be worth the money. That means of corse you will need two different bulbs. By the way, metal halide do not come in 600w. Its 400 or 1000. I have friends who veg under hps and do just fine. You will need an exaust vent/fan to pull out the heat in a set up that size.