I find any of these three cruise lines to be very acceptable. I would make sure that Glacier Bay is included in any Alaska cruise I took. None of the glacier days are as amazing as Glacier Bay. Sitka is my favorite port city in Alaska.You may also want to weigh the pros and cons of sailing out of Seattle vs. Vancouver.
You can save money if you are in the U.S. by sailing out of Seattle but you will miss out on some of the inside passage views. I've done both and have started sailing out of Seattle just because it is easier and cheaper to get to and from.
Overall Celebrity, Princess and H.A.L. are the three mainstream cruise lines we prefer. They always vary a bit but are generally of fine quality and good value.