From an EV perspective, the Volt (any model year) is a better car as it won't start the ICE until the batteries run out. The Clarity PHEV needs both the electric and gas motors under heavy load. My 2017 Volt can handle all loads on either EV or ICE alone.
From a creature comfort perspective, the Clarity PHEV is definitely better.
From the perspective of documenting vehicle operations and maintenance, the Volt wins hands down. GM tells you under what conditions the car will automatically turn on the ICE (there are a few), how often the car handles ICE engine and fuel maintenance, and gives you a printed service schedule. Honda hides all this stuff with the highly paternalistic attitude that says they think their vehicle owners are idiots. (I suspect this may actually be a Japanese cultural thing.) Honda even hid the service schedule from you behind that idiotic "Service Minder" system - you have no idea which service is coming next, which would be helpful in planning for a long trip.
2018 Honda Clarity Touring PHEV - Forest Green w/Tan interior (wife's car)
2017 Volt LT - Heather Gray; black bow ties, Charcoal VoltShelf
2012 Cruze ECO MT (hail totaled 5/8/17 103,600 miles @42.5 MPG)
2010 Mit Lancer GT MT (traded for ECO @31K miles)
2002 Pont Montana AWD - title to son at college graduation
1990 Pont Transport (traded for Montana @240K miles)
1986 Fiero GT MT (traded for Transport - needed more seats)
1985 Fiero 2M4 MT (traded for Fiero GT @8K miles)