There are so many things to consider for Alaska cruises. Round trip vs one-way? Based out of Seattle or Vancouver? Does the itinerary go to Glacier Bay or not (and does it matter to you?)?
Princess and Holland America are the two biggest Alaska cruise operators, meaning they have more ships so more choices, and they have more “slots” to go to Glacier Bay (not every ship gets to go there, and have to do other glacier areas).
We did a cruisetour on RCL Radiance of the Seas (almost as big as the Disney Magic), starting from Vancouver. A 7 night northbound cruise was followed by 5 nights on land, going to Seward, Anchorage, Talkeetna, Denali, and Fairbanks. We had a wonderful time! Alaska is not a place for the RCL Oasis-class behemoths. We chose RCL because that’s who we usually sail with (cost, features, loyalty program, a Visa rewards card). We splurged by choosing a one-way with a land tour, in order to do a lot of Alaska, not just the southeast “Inside Passage” region.
Roundtrips make it easier/less expensive for airfare. Ones that start in Vancouver go through more of the Inside Passage (which has smoother water, more like a river cruise). Ones that start in Seattle tend to spend more time in the open ocean water and stop at places like Victoria on Vancouver Island to meet the “go to a foreign country” requirement of US cabotage laws (modified this year due to Covid so they could do Alaska cruises and stay out of Canada).
The focus on an Alaska cruise is Alaska (land and sea), not the food, entertainment, nor activities. Dress is more casual. Spend your luggage space on layers, not formal wear. When in port, go on excursions that really let you see and experience the place - glacier viewing, whale watching, scenic train ride at Skagway, walking along the narrow old mining-town section of Ketchikan, etc. We enjoyed having a balcony on our starboard cabin, so we could face the shore more than open ocean once we were beyond the Inner Passage. Bring binoculars! In fact, bring a pair for each of you.
We had a great time, with near-perfect weather (usually it’s too damp/cool/misty). We had good, clear views of Denali over 3 days, which is often hidden in clouds. We saw pods of whales “bubble feeding,”
On the one hand, we’d love to go back. But on the other hand, we had such a perfect trip that we’d hate to go back and have a crummy one due to weather or animals not cooperating.