The huge disadvantage with II is that while you own an awesome unit that would command great exchange power on II, you don't get control over what SVN deposits on your behalf. They may deposit a low season week at Kierland or Avon instead.
The huge disadvantage with SVN is that owners lose their view when they trade into another location. I paid a premium for my OF unit at WKORV-N and I'd be stupid to exchange it for a mountain view in Cancun. If I were able to trade OF for OF, I'd consider doing it in a heartbeat.
So I plan on using II only to book great values that they offer from time to time, but will try to direct exchange, rent or give away my unit rather than considering depositing it with II. I doubt I'll use SVN at all, unless it's to a location where view doesn't matter, such as Kierland.
So, if I were you, I'd book a week during spring break (or some other high demand week) at Kierland so that I had something substantial to direct trade or rent on my own should I not be able to get into Harborside. You might also consider putting an ad on this site in late November for a Harborside owner to exchange with.