On Option B, you do not go to Glacier Bay? That is weird. I have only one 1 cruise and it was to Alaska and we were lucky enough to have picked an option that included Glacier Bay.
Glacier Bay is awesome. It was the highlight of my cruise and we are going again next year and I will not do a cruise that does not include Glacier Bay. In this case, our cruise next year will be a Southbound just like your Option B with Glacier Bay and not Icy Strait Point. So anything that includes Glacier Bay is a must for me. YMMV
I am confused about your Option A since you say you are doing a Denali tour. If you do Option A, are you flying to Alaska, do the tour, then fly to Seattle to do the RT cruise? Seems weird.
Another plus on the one-way trips to me is that you get more time in the ports vs the RT from Seattle or Vancouver from what I saw.
A negative with the one-way trips is that you are out in the ocean more. So more changes of rough seas and potential sea sickness.
Hope that helps from someone who has only done a single cruise but is currently going nuts planning his 2nd.