The one million dollar question indeed. It's like choosing between a root canal and a coloscopy.
If you decide to go with II, call Starwood and they'll activate your "request first" (which is really just a "request" but, heck, we can pretend that we believe them when they say it's still a "request first."
If you decide to go with RCI or an independent exchange company, you'll need to book a week first. No need to tell Starwood of your intention to deposit it. Just get a confirmation number and then deal directly with Nurse Ratchett, I mean the exchange company.
For the records, I have never had anything but the hghest praise for II until now. The fact that they are permitting Starwood to control non-SVN weeks and bastardize the request first process has landed them on my hit list.