Width ain't everything. As long as the engine is up to snuff there's no reason a slick 40 couldn't serve you well on many group rides. It's more about the tread/rubber/build for on road speed. There are slick, lightweight 35-40 size tires that will absolutely outperform a 32 cyclocross tire, because of their lack of tread.
Hell, I have smooth 2.35" wide tires which seem to roll easier than a knobby cyclocross tire.

I'd go more volume and less tread for on road, where reasonable. Every time. But I really like some knob if I'm doing spirited off roading (you can limp wrist it off road with just a slick tire most of the time). Might need two sets of tires and need to get fast at switching them out