Just returned this past Tuesday from Thailand, and had spent a week in the time share that adjoins the J W. I really love this property. I have also stayed at the Ren, a few years ago, and was upgraded to a lovely big suite on a paid night, not one on points. The Ren is smaller, newer, more modern.
Either one is a great place to stay.
The location of the J W is slightly better, as it is within walking distance to the Turtle Village, where you will find food and shopping, and it is less expensive than on the J W property. There are free shuttles from both hotels to the Turtle Village all day long. It's just a bit further to ride if you are at the Ren.