The Klits power

Wlad has one punch ko power in both hands hes probably even the hardest puncher in the sport today
Vitali hasnt

 

As said above Wlad does, Vitali doesn't. I don't think either of them really punch their weight tbh, Vitali through lack of technique-which could be to do with his former career in kickboxing, I've heard several trainers comment on ex kickboxers having difficulty learning to properly plant their feet. You don't see much in the way of twisting the knee of hip when Vitali throws, he mostly arm punches.
With Wlad I think it's through hesitation to plant and really go for it. Even Lewis who was always percieved as overly cautious would set himself against an opponent coming forward far more readily than Wlad does. Wlad typically put's the power down when his opponent becomes so frustrated that they mentally cave in and either stop advancing, stop punching or both which tends to be beyond the halfway mark of a fight.
Another point is neither of them are comfortable with short punches or uppercuts and always want their opponent at full-extension range so they're always set to move rather than planted. That's not a criticism, for guy's that big it's the logical thing to do.
They also both have the mentality that a win is a win and they're always in great condition so I doubt they even think twice about a fight going into the late rounds.

 

Vitali might have if he didn't arm punch. He probably doesn't want to slow himself down any further, though, incase he stops.

 

they probably do but neither seems to fully commit or fully sit down on there punches , they hit hard enough though

 

Wlad definitely does. Check out his KOs of Austin and Chambers among others. Vitali may have had power in the past, but now he mainly arm (or arrum) punches and doesn't show a great deal of power. Most of his recent stoppages (and all of them since his comeback) have been more to do with the opponent being outclassed than Vitali's power.