We have been on both inside and outside cabins. I always perfer balconies but sometimes it depends on the cost and time of year as well as location. Balconies are great for sea days and warm weather. I like to sit on a chair and read a good book. Very relaxing.
On the excursions, it just depends on how limited it may be. For example, the dolphin swims fill up quickly and are limited as to the number of people, so we book that through the cruise line. For others, we mostly just hit the people at the pier (to go to the beach for instance). A lot of places also have local vendors that you can book online. However, I don't know a lot about those.