I have been on the Conquest but not the Rhapsody. So I really can't say which is better. The conquest is almost twice the tonnage however. So if you are looking for a big ship, that would be the choice. If you like the smaller more personable ships, then go with Rhaposdy. I'm not totally sure I understand your question about having seating outside. The buffet table area is all inside. There is glass all around but you can sit by the window and watch the ocean go by. You can also sit by the pool but even then you still don't have open rail, its enclosed. Not sure I would want to eat out in the wind while cruising... maybe you will enjoy being able to dine/see the ocean and be in airconditioning too??
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013