HarlieJ - You'd be getting "SPD" mountain clips for the moutain shoes. Note - Not "SPD SL" (shimano) which are actually road clips. I'm not sure there's a huge difference in power. Mostly, road clips have a larger surface area that your feet rest on. For longer rides, it distributes the pressure better and will fill more comfortable. For most triathlons, other than IM, I'm not sure it'll be such a critical factor.

With regard to commuter shoes and the original poster - I'd suggest a regular mountain shoe rather than a commuter shoe. It'll be a better all around shoe for triathlons and commuting.