Depending on the ship and the port you leave from, on formal night you will see about 5% of the men in tuxes, 80% in suits and the rest in khakis with a shirt and tie ( or no tie).
The percentage of tux to suit varies but man will be perfectly comfortable and in place in a suit.
I always wore a Kasper suit (skirt) until I found my Albert Nippon black vintage pantsuit at a Second Hand store for $37.95. love it!!
Flowing palazzo pants with a beautiful accordian top w/chiffon sleeves that had never been worn ($400.00 brand new).