Nice bikes!

The handlebar and hood setups look very different. The Di2 hoods are angled up more, and the bars have more of a traditional shape and drop to them. This seems like it would affect comfort, no? You should try running the same bars and hood setup before making any final judgment on comfort IMO.

As for being faster on the Tarmac, that is not really surprising. Not only is it stiffer and lighter, but the shorter head tube combined with more handlebar drop means a more aerodynamic body position.