In my experience:

Riding a Roubaix back-to-back vs a GF01, the Roubaix was better.
Riding a Roubaix back-to-back vs a Domane, the Roubaix was better.
Riding a Roubaix back-to-back vs a Synapse, the Roubaix was better.
Riding a Roubaix back-to-back vs a Defy Advanced, the Roubaix was better.

By "better" I mean from a comfort standpoint (which is the point of "Endurance"). The Synapse was a bit more nimble (it felt more like a Road/Race with some Endurance comfort) but otherwise all the bikes were pretty close (just not as good at reducing road buzz/bumps as the Roubaix).

I was interested in the Volagi Liscio but all the lab tests suggested it was pretty wobbly (which might add to comfort but there's a certain point where you start to lose stability and it's not worth it IMO). It would have cost $200+ to order a demo bike since there are no LBS for them around here so I skipped it.

I was also interested in the Bianchi Infinito CV but once again there were no LBS that I could demo it at. Maybe someday.