We own at Riviera and love it. I do think you need to own there to get SV rooms, and especially for the tower rooms. The current VGF deal is excellent, and it's a beautiful resort. I think direct to get access to discounted APs (when they come back) for a young family is a valuable perk, and being able to use VGF points at Riviera/Poly 2/DL Tower, etc., is worthwhile. You can't go wrong with either, IMO, but I definitely suggest buying where you want to stay. It's very hard to get a full week anywhere at 7 months out, so home booking advantage is a real asset.
I also think the Riviera resale restriction hysteria is massively overblown. It's selling for $145-$155, and most of those were probably bought in at the $165-$188 range. I don't think that's bad at all, but just my two cents.