Tri bike or not to Tri bike?

what are you saying?

get a sub 1000 used bike or get a couple year old tri bike?

Isn't that about the same thing.

If you have money to spend, a tt bike is nice. More comfortable geometry and generally more aero.

A modified road bike would work fine too

Most consumers in recreational triathlon don't understand the three largest benefits of a triathlon bike in a non-drafting setting for an event when you are running off the bike:

1. More aerodynamic body position.

2. More stable handling.

3. Faster run split off tri bike than run bike.

Here's the issue; along the spectrum of excellent bike positions to poor bike positions tracks a parallel set of opinions to debunk each of those. Most people who say "don't bother" do so because they either don't fully understand the answer to the question and/or never used a correctly fitted triathlon bike long enough to acclimate to it and reap the benefits.

There is no such thing as free speed. The bike has to be optimally positioned, fitted and you have to be acclimated to the bike. One year. 365 days. 12 months. That's right. And there is your reason why so many people will opin, "Just get a road bike and bolt on aerobars" and "My tri bike is squirrely to handle."

Unless you're willing to meet the equipment half way with hard work and due dilligence your experience on a tri bike will be less than optimal. You have to put in the time.

It may be better to just stick to the road bike.

If you can stay comfortable on the road bike , go  for it

2 reasons the Tri bikes have steep seat tubes though is to 1) put your hips at a less severe angle when you are doubled over and in the aero bars,   2) the more upright seat tube is supposed to work your legs a bit different so you don't completely lay waste to your running muscles --

  a couple of companies used to make reverse layback seatposts to somewhat convert a road bike over- maybe they still do - one was Profile

but if you experiment with your road bike and are satisfied with your running performance after a long bike split-- may as well save the $$$$ i guess ---

"...a couple of companies used to make reverse layback seatposts to somewhat convert a road bike over- maybe they still do - one was Profile."

Absolutely correct.

One issue with the forward bending seatposts like the Profile Design Fast Forward, the Thomson or the Sugino is they move the rider's center of gravity very far forward really disturbing the handling of the bike.

A bike is a peculiar vehicle. It is normal for the payload (us) to weigh ten times as much as the vehicle. As a result, a small movement of the payload on the vehicle creates a dramatic change in the handling. In the case of bringing the rider forward on the saddle the weight bias moves onto the front wheel making the steering more responsive, the opposite of what you want.

If you look at the head angles of triathlon bikes- well designed ones- and compare them to road bikes the trend will be that the triathlon bike head angles and front-center dimensions (distance from center of bottom bracket to center of front hub) are shallower and longer. The tri bike is built for stability in the aero position. The road bike is built for nimble handling in a group.

It's no wonder road bikes don't work well with aerobars. They simply weren't made for them. As triathlon bike inventor Dan Empfield said, "A tri bike is designed from the handlebars back".