I think you're better with the BMC. Sram red is way better (both in value and effectiveness) than 105. The carbon tech has not upgraded that much since 2011. Speedplay pedals are welcome too, best pedals on the market IMO.

From the looks though, I prefer Argon18 paint and geometry. I have an old Argon18 and it rides great. (pay attention to the screenshot though, this is clearly NOT what you'd get from a 105 argon 18!)

So both good choices, but you'd get more bang for you buck with the BMC.