@OmSigDAVID,
Well...I would say far less.
Average boxer, let's say an average heavyweight boxer, it really wouldn't be fair to compare a middleweight or a lightweight to one of those over developed fellas {they can get pretty heavy} that's why they have different weight classes. Generally speaking, small guys punch very fast, but there is not a lot of weight behind it, big guys...punch slower, but generate a lot of blunt force....where these two lines intersect, I couldn't tell you...but I'd say probably someone like Evander Hollyfield, would be at the x...he was a light heavyweight, but worked his way up to heavyweight...retaining plenty of speed, and a bit more power with the added weight.
Bodybuilders, are more bulk than anything, {just watch them walk up to the stage, they waddle up} but I suppose if one were to stand flat footed and throw a roundhouse or a haymaker...big wild swing...sure, they could hit with a lot of force....it would hurt....but again, muscles that are disciplined for throwing punches, will allow the boxer to actually hit harder, even though the muscles are smaller....a 155 pound middleweight might even be able to punch "harder" as well....maybe. The biggest guy doesn't always win, I've seen little guys climb up and all over a big guy in just a few seconds...fight was over...I know a few little guys...and it's just the way they are built, and the way they carry themselves....that I would not want a piece of.
Kimbo Slice, comes to mind...he is pretty beefy, but he is more of a brawler...boxing is an art...the sweet science and all that....I wouldn't be totally afraid to climb into a ring with a real boxer, I ain't scared of Mike Tyson, I can bite too....brawling, straight up fighting, is not the same thing at all....I would never, ever want to go toe to toe with Kimbo, not even with a 2x4. A body builder though....eh, just push them over and watch them struggle to get off their back like a turtle.