I have not done an Alaska cruise with
DCL, but I have done both the Alaska
ABD and an Alaska cruisetour with Princess.
They are very different trips. The DCL cruise (and most Alaska cruises) stay in the very southwest corner of Alaska along the Inside Passage. While this area is very cool, and worth seeing, it can't really hold a candle to inland Alaska (Denali National Park, the Kenai Peninsula, etc). When I took my cruisetour, the cruise part was nice (especially cruising Glacier Bay), but the best part of the trip was definitely the land portion that went inland to Fairbanks, 2 areas of Denali National Park, Anchorage and the Kenai Peninsula (and included rides on the Alaskan Railroad).
The Alaska ABD also does Anchorage, Denali National park and the Kenai Peninsula, and a very short ride on the Alaska Railroad.
Personally, if I could only do one trip (an Inside Passage cruise vs the Alaska ABD) I would definitely choose the Alaska ABD. But that's just me. You know your family best. The best would be a trip that included both!

If you're looking at taking a cruisetour with another cruiseline like Princess, then that's a whole different story.
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