I don't think the broker makes that much difference. True it makes a big difference if something goes wrong but that's rare if you do your due dilligence. Frankly, I'd go with the cheapest option that fits your needs. I've bought 3 and none through the usual talked about here. One of the problems with the usual ones discussed here is the prices tend to be higher though with the recent ROFR issues, that's less of a problem than it was 18 months ago.
Just verify with DVC (with the seller permission of course) the number of points owned and points accounting. The easiest for DVC is to have the seller get a points acccounting and then send it to you.