I'm sure you would have a great cruise on either ship. We just returned from a cruise on the Explorer and we really enjoyed the ship with all of the activities. I would highly recommend that everyone (regardless of their cruiseline loyalties) should experience one of RCI's VOyager Class ships. They are amazing.
You're best bet..EXPLORER!!!!! There is so much to do on this huge ship. We have sailed on her two years in a row. We have tried Canival and hated it, others we know had a good time on them. But you MUST try the Explorer, it's the best cruise we ever had. That's my opinion and I'm sticking to it!