I don't think there's much to suggest Adamek hits harder than Jirov. Adamek was the more textbook and sharp with his straight right. The knockdowns against Cunningham were sharp, short right hands that landed right on the button. Jirov looks like he throws slapping shots (similar to how Adamek looks when he's throwing flurries), but his slapping shots looked and sounded like they hurt. In my opnion, Adamek was faster and more accurate with placing his short shots on the chin or wherever, but didn't hit harder. Adamek definitely knew how to deliver that straight right to the jaw though that's for sure.
Take a look at the first couple of punches Jirov throws against Toney in the first round. you can hear the thud on all of them. When Toney lands they are sharp straight punches but they don't look like the kind of heavy shots you get when Jirov lands. or at least that's the feeling I get. (starts at 7:05)
To compare Adamek and Jirov to similar looking opponents:
Adamek has the boxing approach whereas Jirov has the attack the body and destroy approach, but you still see a difference in power.
Here Jirov stops McGroom with one well placed left to the body. McGroom went 10 rounds with James Toney in a close fight.
it's actually hard to say who had more power, whether you count delivery/accuracy and speed, but in terms of raw power it goes to Jirov.
that's the way I see it