Have stayed at both, own now at SVR.
SVV is a somewhat smaller footprint, although it has a higher density of villas. If you remember the larger Lakes or Cascades buildings at SVR, that is what all sections at SVV are like. Depending on how you look at it, this can be a pro or con; some like the big buildings with elevators and parking lots, some like lower density with the ability to park at your door.
SVV has a nice pirate ship pool and a bigger waterslide; not sure that this is an attraction for your age group. SVR has more pools, a couple of pools that are more popular with the teen/tween crowd. That's a plus for us - kids can hit a noisy pool, adults can relax at a quieter pool.
SVR also has more sports opportunities for that age group (basketball, tennis, mini-put, beach volleyball, etc). There are basketball and tennis courts at SVV too, but they aren't as well located, and the bigger population at SVR means you see more pickup games going on.
SVR, just being bigger, has more on-site dining and a bigger Marketplace. SVR is older in start date, but they finished building around the same time (their development periods overlapped) so it is not like SVV is that much newer.
SVV is a negligible 4 minutes (estimate) further from the Disney parks - but 4 minutes closer to SW and USF. Both have dining options nearby, although none are really walkable from either.
I guess that the biggest difference I see is that SVR just has a bit more of everything, including space. If you found SVR too spread out last time, you might enjoy SVV a bit more, but some amenities can still be a walk depending on where you stay in the resort.
To my mind I would let price be my guide. You can't really go wrong at either.
