If its for SPS, I would use snails, but not hermits, crabs or shrimp... this way you can bomb it with interceptor if you ever have a red-bug outbreak and not worry about anything.
Its not really about a QT with better lights though. Often, they are shorter tanks... sometimes wider as well. This allows you to use a single halide to light a much larger area since the light doesnt have to penetrate as deep. So the halide can be raised up higher... and this also means more coverage, so the tanks are usually designed to take advantage of this... like 4' wide by 4' long, and only 12" high.
The long, short, and wide frag tank also makes it easier to get great flow... as a powerhead or pump outlet can generate a beam of flow reaching the full height of the tank, top to bottom, and then over a long horizontal spread as well.
The large surface area of these tanks also makes them ideal for 'look down' viewing, rather than from the sides. This helps sell corals better, as they usually look better from the top then the sides... esp with clams.