I just had my first experience renting points for a villa at the Poly. I started about 10 months ahead of my desired dates, and had I tried to book dates for a trip any sooner than that, the company I was working with wouldn't have even accepted my request (it's that popular!) It was definitely a learning experience for me! Even when I *did* book, they made it pretty clear that what I was requesting was pretty popular, and there was a small possibility they wouldn't be able to secure my reservation. It ended up taking about 2.5 weeks of nerve-wracked waiting before I was notified that it had gone through! My suggestion- start as early as you can. I am *so* excited, and the savings we made by renting points were well-worth the stress.
As far as choosing between the two- I'm probably not super helpful there, because my aesthetic made it a no-brainer for me. I am a die-hard fan of *everything* Tiki and Polynesian Pop, so staying at the Polynesian is a dream come true! The idea of having a nightcap at Trader Sam's without having to travel from another resort (no matter how close, hahaha), is pretty awesome. I just love the relaxed vibe of the resort.
Good luck!