As long as he works!
I assumed that Henry was wet & dry once. Then found out otherwise after sucking a few litres of rainwater out of a flooded car and Henry's magic purple smoke came out.
I think the wet & dry Henry has a blue base instead of red & has a float ball under the motor intake so that when the bucket fills with water it blocks off the intake to avoid sucking water into the motor.
Internally they have a different motor. The dry one blows the sucked in air up past the motor windings to cool them. So if you suck up water with it the moisture in the air will cause a dead short!
A wet vac motor keeps the sucked in air separate from the electrics & uses a separate fan to cool them.
https://www.hillreps.com/vacuum-motors