I did a Norway Fjord cruise last summer. Loved it!
My suggestion is look at the ports. I don't know where
DCL vs RCCL is stopping. Do research on what stops are the best for you and your family. FWIW, we found Geiranger Fjord simply magical!
Also, if you are going for a suite I would suggest looking into Celebrity. As PP stated, suites are in tiers on RCCL. Sea is the lowest and the perks are minimal. Sky offers a lot more but not as much as Star benefits.
With Celebrity the perks for Sky Suite (their lowest on the scale, i.e., Junior Suite) are very comparable to higher suite categories. Of course you don't get as much, but you have a lot more perks than Sea or Sky on RCCL.