I have got both, and for a while I was also very seriously into triathlon. If you are doing the longer races, as well as not racing with the Pro's then that means that you can have a full Time Trial bike for all the races. And to me personally having the aero TT bike was a massive difference over the road bike. You do go faster, and because of the different position it does save your legs a bit for the run. You just have to ensure 2 things when setting up your TT bike. 1 - is that you are comfortable on the bike, particularly on your TT Bars, if you are always off them, then you are not aero, and not getting the advantage. 2 - Being in an aero position on your TT bike, when on the bars. This does contradict a bit in part 1, but if you are not aero and nice and low on your bike, you are not getting the advantage of the TT bike. That is my 2 cents worth, and I had some amazing times on my TT bike.