A lot of good points have been made already but here’s my two cents.
For us, ease of use is really important. Could we manage two separate UYs? Yes but it would add another layer of complexity. This is one of the reasons we bought VGC direct - we knew it would be hard to find a VGC with our UY resale.
Another ease of use is we bought where we want to stay - usually we book at month 11 and are done with the reservation. We’ve switched at 7 months to AUL, to the Poly overwater bungalows (spent 8 nights, totally worth the points) and VGC (before we owned at VGC). We stayed once at SSR - see below, last minute trip. We were thinking about buying a bunch of inexpensive resale AUL with the goal of using them to stay 8 nights in a bungalow every few years (or go to AUL) but decided we’d rather buy less points at VGC so we’d have the 11 month booking advantage.
Location is very important to us. We stayed once for a long weekend at SSR and honestly did not have a good time. When we bought SAP points a few years ago, we bought resale BLT because we knew we’d be happy staying there if we couldn’t or didn’t want to switch at month 7. Some people though love SSR so it depends on what is important to you.
Vacation goals are important too - we initially bought enough for 8-9 nights in our preferred travel times (not summer, not holidays) for a 1BR at our first 3 home resorts (BCV, VGF, and BLT). Our first contract was BCV resale (2009, I think) with enough points for F&W every 1-2 years. Along the way we added VGF (2012/2013) and BLT (2020). Then my FIL died - he and my MIL often would travel to WDW with us and they’d stay in a hotel room while we stayed
DVC. So our new goal became having enough points at our WDW resorts to get a 2 BR LO if she went with us. So we added on 1 contract to each of home resorts for that purpose. We don’t have enough VGC points to always get a 2 BR but she much prefers WDW.
For us, the restrictions on resale and new resorts don’t matter. We have no desire to stay at RIV, the cabins, or VDH. We do have enough points (direct and grandfathered) that we could if we wanted to but we would not buy direct just to avoid restrictions on DVC2 resorts.
In total we have 7 contracts spread over 4 resorts with a mix of direct and resale in the same UY.