Depending on your age and what you're looking at, you might also want to consider Holland America. They've been doing Alaska longer than anyone else, have more ships up there, and own all their own hotels and lodges. (Other cruise lines own their own lodges, but not the hotels.) We did a 14-night cruise tour with them and they took wonderful care of us - we absolutely loved it. We never had to handle our luggage, had a tour guide with us the entire time, and the coaches were great (I'm 6'1" and never had a problem with space). The train was very nice.
While we've done RCCL many times, including the Radiance, which we really loved, we've not done them in Alaska, so I can't answer your specific questions about that. However, we have had alot of clients doing RCCL in Alaska and they've always reported having a wonderful time.
Of course, it's tough not to like anything about Alaska!