OP...get the Tarmac hands down...especially coming from off road. Ride is better...and aero benefit only shows up if:
1. your riding position is very aero aka aggressive...probably not the case coming from off road.
2. you ride high speeds with big watt expediture. Unless you live in the 25 mph zone, the aero benefit between the two is nebulous.

Further...you don't plan to race. The Venge is more a purpose built bike...and a Tarmac is a better do it all road bike.

Btw, If you ride upright, the Roubaix is best of both and there is nothing between any of them in speed...about the engine.