I am also new to MH and I am buying two IceCap pendants and modifying my canopy so that they will hang level with the top. I really do not see them as that much more expensive.
The IceCap pendant is $180 + bulb each and includes remote ballast, insulated housing, reflector for light spread at the aquarium only and choice of 250W or 400W. Packaged comes in a nice finish.
The HomeDepot fixtures are $90 on average + bulb and are going to be heavy construction (designed to take a beating plus locally mounted ballast), not insulated (will put a lot of heat into the house and tank), come in odd wattages (bulb limitations) and the reflector is designed for 360 degree spread of light (means you will need a higher wattage to get a similar effect as a lower wattage aquarium fixture). Unless your tank is going to have an industrialized theme to its setup (which would look nice if done properly) you will need to do a lot of modifications to make use of the fixture, DIY a canopy and it will still look uhm....out of place...and all you saved was about $90 a fixture.
Personally, I like IceCap but they are not the cheapest. This board has several threads of excellent online vendors to put MH systems together at about $100 a fixture w/bulb and it will mount right into a DIY canopy...or about $150 a pendant w/bulb and forgo the DIY canopy.
My 0.02 cents.