Based on what I've read AND experienced...
A verandah room can help, shouldn't hurt.
There seems to be different forms a sea sickness, and one form is when you start getting a sick-feeling headache because your "ears" can feel the motion of the ship, but your eyes tell you everything is still. For this situation, seeing the motion of the boat helps.
We always seem to get sea-sick the first night on the ship, and it's usually when we go see our first movie (no windows but you feel the motion of the ship), or dinner.
Come to think about it, we've been in both inside and verandah rooms, and I don't think our rooms ever contributed to our sea-sickness. We seem to initially get sea-sick when we are in a large open space (theater, dinner, etc) and our eyes say "look, our WORLD is still" but the ears say "we're moving". But when we are in the cabin, it seems like our eyes say "I can't tell if I'm moving or not because I know this little cabin is not my whole WORLD". But when you're in a large space and can't see outside at all, the eyes say "this is my whole world".
Sorry to be rambling on...
bottom line advice, get a verandah room if you can afford it just because it's a verandah (only use sea-sickness as an "EXCUSE" if you want to privately to help justify the cost to your self).