The motion on a cat in a seaway is quite different than a mono. I haven't been seasick in 30+ years but my first time making a passage on a cat I was queazy for the first 24 hours. You can't beat the room and if you are planning to charter in the BVI's or other sheltered waters it may be the way to go.

Drink all day at home, your friends worry about you; do it on vacation and they say "what a good time you're having". Save your friends needless worry, travel more!