In many instances, I prefer inside staterooms as they offer many advantages. Don't worry about the location of your cabin, rather worry about the ship that you select. Genarally, you should book a cruise when you have made up your mind to go. If there is strong demand for the cruise, it will sell out leaving you without a cruise. If there is weak demand and the prices drop, your travel agent can generally get you an upgrade to a better cabin, or the lower price.
What ship and itinerary are you thinking of?