I’m short on cash. which one do you think is the right choice. the cervelo dual with ultegra or the P2k with shimano 105’s. could always upgrade the p2k later, right??
I’m not the xpert, but I’ve had a lot of people tell me that 105’s are perfectly fine for racing. I’d go with the P2K for sure.
The Ultegra won’t make you any faster than 105 but the P2K frame is a bit faster than the Dual due to the rear wheel cut out and a faster fork.
I have bikes with 105, Ultegra and Dura Ace. Other than a slightly shorter shift on the DA STI, I can’t tell the difference.
My 105 group is six years old and still going strong.
What about getting the Dual w/105 and getting a set of aero wheels. Might be a good plan.
Brett
P2k - hands down. Then when you get some $$$, uprade to Chorus 
A couple of years ago, I had three 'cross bikes, one Ultegra, one 105, and one Dura-ace. The shifters on the DA bike and the 105 bike made it through the season, the Ultegra got replaced twice. All three bikes were used roughly equal amounts of time; the idea was to test the components for spec on production bikes.
I came away from this believing that DA is way better than Ultegra, and 105 is roughly equal to Ultegra in functionality, but is heavier and has significantly greater longevity.
I was using shift components only - there are better alternatives to Shimano for all the other components in the 105/Ult. price range.
just FYI, we found Campy Chorus to outlast DA nearly 300% on the cross bikes - DA was good for roughly a season, and the Chorus from that years bikes is still running strong (rode to work on it today, as a matter of fact…)
MH