Cain is taller, longer, heavier and has much better cardio than Cormier.
Here are some stats from their fights.
Jones vs Cormier: Jones threw 215 strikes and attempted 5 takedowns.
Dos Santos vs Velasquez 2: Cain threw 339 strikes and attempted 33 takedowns.
Velasquez vs Dos Santos 3: Cain threw 378 strikes and attempted 13 takedowns.
Now I know fighting isn't just about work rate, but that says a lot. Jones has issues with intelligent pressure, Cormier showed that. Cain is the best at pressuring intelligently.
It would be a tough fight but I see Cain beating Jones, either by decision or late round stoppage.
I posted this in another thread, just edited some of it. Cain would be constantly mixing it up. Jones was very impressive against Cormier, not because he dominated but because of how he adjusted later in the fight.
But Cain is a beast, he'd be too much for Jones and to be fair he is too much for everyone at the moment.