Not to mention that the light holds I've seen demonstrated put your handheld light right up against your pistol anyways. The idea that you'd stretch your light and arm all the way out seems... dubious.So you prefer shooting 1 handed then. Only in places where there are no doors to open or things to hold on to.
As for the particular light, Surefire, Streamlight, Insight, or Inforce. Lots of good choices in those brands.