I had 2 tri bikes, I sometimes do duathlons(I can't even doggie paddle!). I found while both tri bikes were incredibly fast and allowed my legs to have more of a downward pedal extension, vs a slightly forward extension(road or mountain bike typical BB) which seemed to feel less tired for the run that followed, it wasn't worth the discomfort overall that both bikes had(carbon fiber and steel). I am not really an aero bar person, I swear I have t-Rex arms paired with clown feet, which makes tri bikes fit me weird. I felt like I was being folded in half and I sortof am fond of breathing
So I went back to road bikes with drops and it is much better. My legs feel heavy when I first dismount the bike and take off running but my form overall is better and the small amount of time I loose on the bike being slower translates into a better second run time with improved form and less feeling winded. Plus the next day, my whole body likes me better.
If I became a potential podium finisher, I would go custom CF or Ti so I could get the fit right. T-Rex's don't ride bikes