It would depend on the ages and expectations of your group. Here is how I would rate the ships...HAL, older crowd. Princess, younger than HAL, but older than RCI. RCI is going to have a younger crowd (by younger, I mean that there will be lots of people in their 30s, 40s and 50s)
Also, check the itineraries. If one is offering a 1/2 day stop in Cabo, go with the one that has a full day.
I just got off the Legend of the Seas on the Mexican Riviera itinerary and LOVED it. Since she was built as a world cruiser, she can run fast enough to make the run to Cabo to offer a full day's stay. Everything about RCI was wonderful and I would highly recommend it.
I am working on a MEGA review of the experience, but let me know if you have any questions.