The cruise we took was in & out of Southampton, so a large number of Brits were on board which probably pushed up the number of Tux wearers as there wasn't any weight issues.
I would have to say that about 70 to 80% of the men who wore formal went for the Tux & BowTie, with about 20 to 30% in dark suit & dress tie. There were a few dozen who chose to wear neither, but they were definitely in the minority.
I hope this is of some (if little) help, I'll take a look back through some of our photo's this evening to check my memory of %'s.
On the subject of photo's, if you are interested, we've posted about 100 of them in the photo section
Alan & Katrina
Last: Cunard Queen Victoria January 2016
Next: Oceania Marina June 2016
Then: P&O Oriana August 2016
Then: P&O Oceana December 2016
Golden, Grand(2), Caribbean, Royal, Sea(4+1 aborted)
Adonia(4+2), Arcadia, Artemis(2), Aurora(5), Azura(2), Britannia, Oceana(3), Oriana(12), Ventura(2), Victoria(5)
QM2(2), QE2(9), QV(7), QE, Caronia(2), Minerva, Minerva II, Fred.Olsen(8), NCL Jade, =X= Eclipse, HAL Ryndam, Aza.Journey