DFA123 said:
Weight isn't the only consideration though. A heavier, very aero optimised bike, will be faster than a 400g lighter less-aero bike in many racing situations. The most aero bikes are often around 7kg or more. I'm sure Contador knows that though; but he needs to explain away his failure from last season somehow.
Most bike brands have 3 or 4 bikes: an aero, slightly heavier one for sprint stages (in Speshy's case the Venge, Trek's case Madone), a super aero & heavy TT bike (Speshy Shiv, Trek SpeedConcept), lightweight climbing bike, not as aero (Speshy Tarmac, Trek Emonda) and then both also have a bike specifically for the cobbled classics (Roubaix - Domane). Obviously, aerodynamics don't matter much at all uphill, for climbing bikes any aero advantage that adds more weight, is a disadvantage.
Of course, Contador isn't comparing Speshy's aero Venge to Trek's climby Emonda. He barely used the Venge anyway. He's comparing the Tarmac to the Emonda: Specialized lightest bike to Trek's lightest bike.
Actually, while googling for frame weights, I found out the Tarmac isn't even meant as just a climbing bike, it's meant for allround racing which would explain why Alberto never used the Venge and is using a Madone for flat stages this year. It also explains why the Tarmac is presumably heavier than the Emonda. Still, the issue remains: it is Specialized's lightest bike. And to answer your swipe at Berto that he "needs to explain away his failure from last season somehow",
I'm sure you're aware that 400g makes a huge difference, 1kg lighter equals 30s faster on Alpe d'Huez. So, with a lighter bike, he might have won both Catalunya and Paris-Nice last year.
Unfortunately, I can't find the video in which Alberto talks about the Trek bikes, but I distinctly remember him mentioning that the Emonda is actually below the weight limit (so they need to add weight).