You fuckin me nukka? Use both, if you can handle the heat issues. More is generally better. I would save the second 1000W, the HPS, until those plants are a little more mature so they can actually process that amount of lumens. The MH's spectrum will be more useful in veg than in flower, but during budding, having that MH running is golden; the UVB will greatly stimulate resin production and, from what I'm told, even enhance the high itself. I'm throwing a 1kw MH in with my 1kw HPS right now, I just have to work out the logistics because heat can become a big issue in such a small area.