Ok, I'll bite, starting with the caveot that the differences are small and marginal, and the motor is about 99 times more important than the chassis.

I've had several high end CF bikes, and a number of good steel bikes. My last steel bike was a Waterford built Paramount OS, admittedly you can get a lighter steel bike today, but the Paramount OS is still pretty close to as light as steel gets, and was stiff for steel with oversized, butted, shaped tubes.

It definitely flexed more in the bb, and the front end than my current CF bike, and the frame was 2lbs heavier than my Zero7. As for how that translates to performance, you can quantify the effect of the 2lb weight difference climbing, and accelerating. It's pretty small but not non existent.

Biggest performance difference for me is descending and cornering. The stiffer front end on the CF bike allows me to corner and descend faster. Admittedly, the reason I'm faster is subjective, i.e. the confidence induced by the stiffer front end, but the result is objective.

The difference in speed and acceleration from a stiffer BB is tougher to quanitfy, and is subject to multiple page threads debating whether a stiffer bb is faster. I'll leave it here as stiffer definitely feels faster. Also, I could ghost shift any steel frame I ever had from Frame flex. I've never done that with a CF frame.

I raced the Paramount a couple of times after I got a CF bike. The bike never held me back, other than a couple of sprints, where I believe (perhaps wishful thinking) i could have won on my CF bike, and lost by a wheel length on the Paramount.