Choices suck sometimes, don't they?
Ya know, Craig, people pay big money to do cruises from Seattle to Alaska. And I've known numerous people who have done the ferry who rave about it. You have a big trip ahead of you with lots of driving and plane trips. They always have tales of interesting people they've met and fun activities, like playing cards or board games, etc. with people they've met, people jamming on guitars and other instruments, etc. I think it all sounds like a hoot. I'm thinking this might be a bit a relaxing and enjoyable respite from the go-go-go you're going to have most of the rest of your trip.
But, then again, more time in Alaska might be good, too.
Tough choice but I don't think you can make a wrong one.
Maybe try communal living?
Many people enjoy camping out on deck or inside the common areas and enjoy the trip just fine without having a cabin. I have to admit that I think I'm getting a tad old and cranky for that option myself, but you're a young buck still! Just something to consider. I hear it's a lot of fun.