Don't know your specific interests but for me the Dream class ships have two advantages.
Deck 5 is a great place to spend time with lots of food stations and lots of seating spaces and lots of walking opportunities.
The spa areas on these ships are the best in the fleet. And the spa offers quick and easy access to the Serenity deck through the front elevator accessible from deck 11 and 12 in the spa.
My only recommendation in that regard is if you choose to upgrade to a spa balcony, I prefer deck 11 because the balconies on deck 12 aren't covered.
Oh, I nearly forgot. One deck (maybe deck 7??) goes all the way around the front of the ship. Windy, but beautiful at night.
Happy sailing.