If you can't fly in the day before the cruise departure, I would definitely do the northbound cruise departing from Vancouver. As was mentioned above, your cruise doesn't even depart from Anchorage - it departs from Whittier, which is a 90 minute bus ride or 2+ hour train ride from the Anchorage airport. If you miss the cruise ship departure, you will miss three nights of the cruise at a minimum since the next place you could pick up the ship would be in Skagway (the first two full days are at Glacier Bay and Hubbard Glacier, which are sailing days).