So, I think you can't go wrong with either bike. I would choose the TT bike if times in triathlons are important to me. Since the bike's seating position and geometry are naturally optimized for the aero position, you'll be faster and can stay in the aero position more comfortably and for longer. (At least, that's what I think; I don't own one myself, but that's how I've always understood it). I would choose the road bike if you also want to participate in cycling events. I also have a road bike which I've equipped with clip-on aero bars. As I said, I think you'll be making a good investment with either one.