I tried both of these bikes, and I ended up purchasing the IA4 in December. Factors that influenced my decision:

1. The IA4 fits me perfectly.
2. The clean lines (integrated brakes, cables) are damn sexy.
3. I planned to ride an Attack saddle...included with the IA4, so it saved me $200+
4. The IA4 is the best bang for the buck, IMHO
5. The IA4 is a bitch to travel with if breaking down the front, while the QR is quite appealing in this aspect

I would go with the Felt IA4 because aero matters more to me than ease of use

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Make Inside Out Sports your next online tri shop! http://www.insideoutsports.com/

I'd go IA, because after four years with the old B2 Pro, I feel confident enough in my ability to break down any bike for travel (and then reassemble). I might go with one of the other IA builds, though.

But I also wouldn't discount the PR6. Definitely one of my favourite bikes. I wish they'd produce a stem that doesn't go as high, though.

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ZONE3 - We Last Longer

I looked at them both at one point but since I didn't own a bike case yet I just skipped the PRSix advantage by getting a Scicon Aero Tri case. Now I don't have to take anything apart to travel, and even if I did the IA isn't that bad at all. It's a couple allen keys which I've got in my flat kit anyway. The IA is faster, sleeker and honestly easier to get your hands on for a demo.

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"Train so you have no regrets @ the finish line"

At the beginning of this year I decided it was time to buy myself a "new" bike after having used ones forever.

I ended up going with the IA4 and have not ever regretted my decision. IF it fits you, it's the fastest bike manufactured, but that's a big IF, the bike doesn't fit everyone.

I went to my fitter, said price wasn't an option lets get me the fastest bike that fits me. IA was the way to go in my opinion. My second choice was speed concept and 3rd was the Plasma 5. I also would have considered that new Diamondback bike, but wasn't available for sale at that time and I didn't want to wait.