Already an II Member. Should I join RCI also?

I am specifically interested in HGVC on the island of Hawaii. And it seems that these only (??) trade through RCI.

I have four 2016 weeks to deposit. Normally would just put them in II for Starwood preference for Maui/Kauai. But we want to get to the big island next year (and possibly different resorts on Maui that what's available through II).

Is the biggest thing I should worry about in RCI be TPUs for my 4 units? And how would I find out the TPUs for these units?

Thanks

Already an II Member. Should I join RCI also?