OP, If you're still reading . . . I think the main difference between renting points and booking directly through Disney is the set-in-stone nature of renting. It's something I never really considered, but a couple of years ago, I had to change my WDW reservations three times in a row since we were prevented from traveling during a blizzard. Had I rented points, I would not have been able to change the dates. Perhaps if I had
trip insurance this would have covered this eventuality (I've never had to use trip insurance for something like this, so I don't know), but, as it was, we were able to rebook the trip through Disney. It was easy and it worked. And we got to go. If we'd rented points, we wouldn't've gone, since 3 or 4 nights of the original booking were spent at home waiting for the snowstorm to end. And even if we had gotten some kind of refund from trip insurance, if that's possible, it would have been money but not a trip.
Another factor to consider is: What happens if you have to cut your vacation short? This has also happened to me before, when I got sick at WDW and wanted nothing more than to be at home instead. Yeah, I felt that bad! At any rate, we were able to check out several days early and we did not have to pay for the room (we had a RO reservation) for the nights we didn't use.
Of course, these are unusual circumstances. But unusual circumstances do happen. Because of my experiences, I no longer book with Orbitz, despite the ability to stack discounts, since you have little flexibility there as well, and I would never rent points, even though I'm often attracted to the great savings.
When you book direct and have a RO reservation, you can cancel up to 5 days before for a full refund, or, at worst, be charged for only 1 night if you end up having to cancel at the last minute. And you won't get charged for unused nights if you have an emergency and have to check out early. I prefer it this way, but I totally understand the allure of renting points.
There are other advantages to booking through WDW, like daily housekeeping (although many people don't care about this), and something that I rarely see discussed on the boards, which is that if you check in and you're unhappy with your room for some (or any) reason, when you book through WDW, you're free to speak to the front desk--it's your reservation not someone else's--and try to get things satisfied/changed/rearranged/rectified, etc. Let's say I check into Resort X and I've never stayed there before and I'm unhappy with it (for whatever reason). If I booked through WDW, I can at least
attempt to change things, move to another resort, another room, another
something. Yes, it might not work out, but at least I can try. If one has rented points, this couldn't be done. Just some things to consider.
I'm not advocating booking directly through WDW. I'm just describing why I personally prefer it this way.