One thing with Alaska unlike the Caribbean, is ALL the ports are worthwhile AND very different. I suggest you find out what each can offer your, THEN book a cruise with your priority. You also would be best to put the glacier choice as well into the mix.
Head to your library and take out Alaska travel books, Fodor's Alaska and Frommer's Alaska are especially good. Look over cruiseline shore excursion lists, available on line. There are only 6 Alaska cruise ports, so it isn't going to be a "big" job to find what may be the most priority for you.
In an overall Alaska cruise selection, first determine what route- one way or round trip, with any one way, strongly consider adding AT least a few extra days- how often are you going to get there???
Look at ports, time in ports, glacier, ship naturalist, price. Budget for excursions, you get only half a trip without them.