You know what? It will depend on the size & wavelength of the chop at a given moment.
Forth cruise last year we exited form under the Kinkardine bridge into a huge wind vs tide chop. SR4, me @ 5M and another 6& a bit M. As the river widened and the current dropped, the wave shape changed. There were times I could motor along quite happily at 25 knots, the others were either slamming big style or over one, through the next.
500 yds. later I was slamming big style, the SR4 was happy, another 500 yds. later.... you get the picture.
You'll have seen the pics from ERR2013. I managed an average of 20,.2 knots to Crinan, 18.1 on the way back, and I'll tell you for free it was hard work for chunks of the return trip, but as Mustrib says, there were times when opening the throttle made it a far smoother ride.
Just remember to stick with your buddy boat(s).