Ok. First off, if you got ladybugs in your soil you are a lucky man. Ladybuds are preditory insects that eat the larve of insects that eat your plants.
Now, the biggest diff beween those lights is its light specturm. HPS is high in the reds-good for flowering and MH is high in blue-good for veg.
I would suggest 2 150 HPS and maybe a couple 6500k CFLs for supplementation, for flowering. I dont know what your situation is but im assuming you have a seedling/cloning area, a veg area, and flower area, each with their own lights.