Actually I just remembered that Lucius stresses that they have gained nearly immortal bodies
The only other way we've seen someone gain a nearly immortal body is by becoming the devil, aka Zenon. Lucius also stresses that they become new higher lifeforms. I definitely have them over devil hosts, that's for sure. For devils it can be more debatable. My reasoning is that Lucius could have remained a devil, per se, by just consuming the devil heart, but he choose to do this. Now there definitely is some benefit to it imo.
The way I see it these paladins will be devils in human form.