I wouldn't worry about weigh much and if those were my two choices I would probably go with the Trek because of all the different options for storage. The draft box is a great option on the Trek and since Felt has yet to come up with a good bento or rear storage I would go Trek. I have a Felt DA but a Speed Concept is always high on the list of go to bikes. But Desert Dude might chime in with his thoughts as well as others with more experience with them both.

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The Felt has much wider tubes. They are focusing on the airfoil and aerodynamics on the frame more than the Trek. That is driving weight. Trek has better aero storage (for now). In many ways, the two are very similar when you account for the trade-offs and differences. Personally, I love the looks of the Felt.

The Felt is fairly hefty alright. A fair chunk of that is the stock wheels which are no lightweights. I don't know how they compare with the equivalent Trek's wheels.
The Felt frame also has a lot of surface area, possibly the most of any tri bike and that material adds weight.

However, I don't think weight is such a big deal for a tri-bike. It wouldn't be my first concern.

This is a great point. I would compare frame-to-frame weights, because the Felt has some pretty heavy components. And, I would not sweat the weight differences either. I have upgraded every part on my IA16. I dropped more than 1.2kg (2.7 lbs.) total. About a third of that drop as in the wheels alone. The next third was in the cockpit. Then, the crankset made up most of the remaining third of weight drop.

Agreed that extra weight isn't a big concern-- provided it yields some added benefit. What is that benefit? Is there any data to support that the bigger IA frame is more aerodynamic. I've looked for head to head wind tunnel testing but haven't found any. I suspect any answer is going to be a mixed bag depending upon yaw angle.

I think weight matters more for the average age grouper. A pro is likely going to get the bike up to speed quickly and keep it there. At that point, absent hills, weight is a non-issue. But the amateur is far more likely to lose momentum at multiple points along a race.

Owned both bikes. IA4 with Ultegra DI2 and Trek Speed Concept 9 with the same components transferred over. There was about 1 1/2 pounds difference.

The bigger differences -

Storage
The Felt's top tube storage is built in. No options for change here - Trek has their bento, but put in standard bosses, so I can also run a larger XLAB bento.
Rear tire tube storage - IA4 doesn't even have bosses, so the IA10-14 have an advantage here.

Brakes
Felt's brakes suck. There I said it! Stopping power is fine, but if they get wet they will not return properly. You will have to clean out everything to get then working again. Even had stronger springs and ceramic coated surfaces from Felt. Setup is also finicky. These will need to be redesigned by Felt next time they update this bike, and I imagine they will / are.

Handling
I got blown around more on the Felt. Tube shape, etc... not sure. I feel more stable on the Trek.

Fit / Setup
Trek has way more options, stems (Felt only has 1), etc... This is a hands down winner for Trek.

Speed
They are very close. Can't honestly pick a winner, but if I were in Vegas I would say the Felt is slightly faster. Maybe 30 sec over a 70.3 though, not by huge amounts if any. I have nothing buy my YOY times to compare on this and a gut feeling, so this and $1 will get you a coke.

Theoretically, assuming Felt designed with speed in mind, the IA's bigger tubes should yield less drag. But with these two, because of the dearth of head-to-head data, I would pick based on looks, fit, price, or local bike shop support. If you think one is just awesome looking compared to the other, get the looker. Or, if no nearby shops have one, get the other. yada, yada, yada...

I've had both. Traded the SC 9.9 for the Felt IA1. Both are good bikes. The storage on the Trek is much better, but I just fit the Felt better, so it is faster for me. And....you can't beat the good looks!

I wouldn't discount the aerodynamics of the Trek. I consider myself pretty well informed and I would bet the difference between the two over 40k is less than 5 seconds... and that advantage may well swing toward the Speed Concept.

That said, to the OP, both are great bikes and both are great brands. Neither is a bad choice.

I agree... that is the point of my 2nd post. I would choose based on other factors than likely speed.

You can't judge aero by looking at tube thickness.

exxxviii wrote:

The Felt has much wider tubes. They are focusing on the airfoil and aerodynamics on the frame more than the Trek. That is driving weight. Trek has better aero storage (for now). In many ways, the two are very similar when you account for the trade-offs and differences. Personally, I love the looks of the Felt.

Sorry but no. That is a false assumption. Not defending Trek or Felt but Felt has to have a larger (and in this case heavier) airfoil because you can't do Treks kammtail virtual foil because there is patent for that shape on a bike. The Kammtail shape allows for smaller airfoil (lighter too) that has the aerodynamics of a larger airfoil. So no Felt doesn't care more about being areo. They just have to get there a different way than Trek. Trek has beat out Felt in several aero test as well....if that kind of thing is important to you.

Both are good bikes.....IMO bang for the buck the Trek is a better buy but its your money.