It really depends on your personal situation. We live in the Seattle area. We have mostly done round-trip Seattle cruises, but have done one each north and south bound, and are doing northbound this year. For us, the easiest way to get to/from Vancouver is using the ship transfer from SeaTac. (I know there are nicer options, but I did say "easiest".) That bus ride is about 4 hours, including the border crossing into Canada, and then we have to deal with going through customs/immigration at the port. The flight home from Anchorage is about 3.5 hours, but without the hassle of a border stop, no customs/immigration. Honestly, I find the flight to be easier than the bus ride, so I'd rather do that at the end.
Of course, there are other factors, such as whether you are adding land days, etc. Many people who do a land tour prefer to do it first and then relax on the ship. Some people like to sail northbound so the scenery builds and glacier days are near the end. All a matter of personal preference.