Tri vs road bike : Again?

This is just me, but... 

(a) MY road bike is a Trek 5500 OCLV Carbon Trek with Dura Ace components.  I bought it used, so I do not know the age of the shimano components, but the frame is a 1996 model.  I had aerobars on there and also rode aero 95% of the time.

(b) My tri bike is a 2004 aluminum with ultegra components.

Hard to say with the age difference which is "better" but the road bike feels a tad lighter.  I was faster and more comfy on the tri bike from day one.   One reason, which everyone seems to ignore, is ease of shifting.  If you are aero 95% of the time, you still need to reach over and shift via the hoods.  The minute I got the tri-bike I was shifting more, at more appropriate times, and riding better as a result.  I live in an area of rolling to hilly terrain, so constant adjustment is required.  

That is a seriously nice road bike.  I liked my road bike too.  I hardly touch it anymore.

I come from a road racing background as well as having been a mechanic and salesmen for 5 years, so have a bit of experience when it comes to cycling.  I also have a road and tri bike, both carbon.  Up until getting into tri I almost exclusively road steel frames (even though I've owned and raced aluminum as well and have ridden just about every material under the sun).

The comfort of a bike in general has less to do with the specific material and more to do with the way it is manufactured/designed.  I have ridden super stiff aluminum that beats the crap out of you and also have ridden aluminum that I thought was going to explode underneath me because it was so whippy!  (If you've ever ridden one of the original Vitus aluminum frames you know what I'm talking about!)  A good builder can make any material do whatever they want with it.

That being said, I like a really stiff but compliant road bike.  I had a Giant TCR carbon bike that met that criteria but recently replaced that with a Scott CR-1 carbon for even more weight savings and stiffness.  But it is a pure road racing bike and is stiff, fast and not very forgiving.  That suits my riding style.

I bought my tri bike strictly for speed and got one of the "fastest" designs out there and could care less about how comfortable it is.  I don't ride it for "comfort," I ride it for fast splits.  With that being said, I've still used it in two separate iron distance races and two HIMs with no issues.

I spend the majority of the time on my road bike and will usually only break out the tri bike as I get closer to an event where I will be using it.  And as mentioned, I get about 1 - 2 mph on a normal training ride with my "training" wheels.  Come race day I use an aero helmet and a disc and deep section front wheel which bumps that average up a bit, so it is harder to compare times between my road bike and tri bike.  I don't "race" the road bike in TT's, so I don't have exact numbers to compare, only training rides.

I don't think you need to spend $4k on up to get an equivalent performance out of a tri bike. In road riding/racing, a lot of the bike's "performance" feel comes from things like the smoothness of a shift, how well it shifts under load, sprinting, cornering... Not things that are necessarily going to make or break the performance of a tri bike.

My roadie is a tricked-up Ultegra (Ultegra + other bits, kind of like tuning a Camaro) titanium Softride. My tri rig is a rigid ti OLD frame with a mish-mash of components mostly 105 level. And I get just as much of a speed boost going from my roadie to the tri bike as the next guy.

In your case, though, I think what you're going to see is the HANDLING difference between being on a road bike with too much weight on the front wheel, to a bike that's actually designed around that position. You're comfy where you are, and that's fine. I think you'll find a whole new level of comfort in being able to relax in ways that you didn't even realize. Go out and try some bikes out and see what you think. In the end, you may decide that making that leap isn't worth the coin. It's your money, spend it how you like.

I have both carbon tri bike and carbon road bike..Kuota K Factor and Orbea Diva..Orbea is much lighter than my tri bike. I ride my Orbea in the winter and with my racing team rides, but spring-fall I ride my Kuota 95% of the time. I love bringing it out in the spring as my pace increases. When I bought it my mph jumped probably 1.5 but end of June my cycling typically jumps so it may be two factors (new bike and fitness) on top of each other.

I have had 3 road bikes set up in tri position..just not the same as a tri bike riding it like it is designed.

We all have various bodies, flexibility and the like. I think key is to find a bike designed to be ridden how you can ride it. My Kuota fit me out of the box built up. Sure I could have gotten a sexier tri bike but it would have required stackers so I wouldn't be riding it like it was designed.

My bike fit guy is trying to get me to buy an Guru tri bike....sweet bikes!