One 250 watt MH bulb is ballpark of 22-23k lumens. So that x2 is 44-46k lumens.

MH is meant for the vegitative cycle...when the plants are ready to be forced to flower...the MH bulbs will have to be replaced with HPS.

Unless you go with 250 watt HPS'...you'll end up having to buy a seperate ballast. Even then, if its not a 'switchable' ballast...one that will run both MH and HPS, you're still stuck forking out loot for an HPS ballast.

Electronic / digital ballast vs. magnetic ballast....electronic ballasts are lighter....smaller...no where near as hot...quiet...produce a more efficient light (they get more out of the bulb) which also makes them more cost effective...flexible in that most electronic ballasts can run either MH or HPS without any conversion...safer with built in overload/surge protection...and generally are nicer to look at than old school magnetic ballasts.

For about the same or only a bit more money at that.