Candi, ask yourself a few questions and you'll have your answer.
1. Will the balcony make the cost of my cruise painful to my overall vacation budget?
2. Do you plan on spending a great deal of time in your cabin?
3. (On the motion sickness issue) Do you have issues in everyday life? *If riding in the back seat of a car, watching a child on a swingset, the motion makes you feel nausious you have an issue. A very small percentage of the population has issues onboard a ship this size. Remember the majority of modern cruise ships are approx 900 ft long. That's three football fields in length. Excluding extremely high seas (in excess of 8' swails) you are not likely to have problems unless you do in your daily life.
If budget is not an issue, get the balcony. If motion is still a concern get a cabin near the middle of the ship (front to back). That is more important than how high the deck is, although it's a tiny little bit more stable lower. All modern ships have stabelizers. Go have a great cruise and quit letting the little fears inside your head make you worry about it.
Next thing you know you'll be a veteran coming here to give us tips.