What are you doing this trip?? You may want different offerings with the next?
Round trip Vancouver trips can be extremely scenic. Round trip Seattle, offer the least scenic itineraries. NCL, last season, did do a trial of Inside Vancouver Island northbound, so would be an added feature to look at.
BUT, overall, do your homework, find out about the various Alaska ports, there are only 6 on the regular 7 day sailings. Find out about the significant glacier differences.
And finally, if going with a one way, I highly recommend adding on time for touring Interior Alaska, I never do these trips without it. In my opinion, more is always better, but it can be best to look at at least 5 extra days, then Denali Park and Seward can be added- wildlife hot spots.
Head to your library and take out Alaska travel books, especially Fodor's Alaska, Frommer's Alaska, Alaska By Cruiseship.