As long as you buy from a reputable dealer and make sure to get the right caliper for your vehicle, it should be fine. Personally I probably wouldn't choose the cheapest brand if there's more than one option, but really you should be fine with anything you get at your typical Pep Boys, NAPA, Advance Auto Parts, AutoZone, etc.
Like others have said though, it's recommended to replace pads (and arguably rotors) in pairs (eg, both sides at the same time). Depending on much material is left on the rotors, you may be able to just have one or both resurfaced ("turned") at a machine shop. Then again, rotors aren't usually too expensive, so if you want to err on the side of safety, consider replacing them both if even one is questionable.