First red flag: do you visit WDW on average every other year? You can make it work if you visit every three years, but it's more complicated and at greater risk of losing points. If you don't visit at least every 2/3 years then DVC is really not for you.
I'm sure you know, but you're comparing two very different things. Club level at the most expensive WDW resort with deluxe dining doesn't compare at all with a DVC studios. Long term you would have an inferior experience (vastly inferior, if you compare deluxe dining + club level) for less money. If the compromises of a timeshare are fine for you, then go for it, but be sure to understand all the differences between an hotel room and a DVC studio.
SSR is going through a refurbishment right now and it will have the murphy bed in all rooms instead of the sofa bed. The same should happen to all resorts, new or when they undergo their next hard good refurbishment.
DVC busy times do not always correspond to WDW busy times. August and Easter, for example, are slow season for DVC and it's easier to switch at 7 months for other resorts during those times. Studios are, however, the most difficult category to book, so it's important that you buy a resort which you don't mind to stay at. If you think you won't like it, then don't buy SSR even if it's the cheapest option. But the new rooms look gorgeous and the proximity to Disney Springs can be valuable for two adults traveling to WDW, I think.
Are you aware of the Riviera resale restrictions and how they may impact the value of your contract long term in case you need to sell?
Have you considered buying resale? I guess you're looking to buy an 80 points contract at RIV, given you look to spend 15k. With 80 points you wouldn't qualify for membership extras (AP, dining and merchandise discounts, special events) anyway and if you don't visit too often probably the extra wouldn't be of great value to you anyway. You can buy 100 points resale at SSR for around 10k, have cheaper yearly maintenance fees and still exchange with all the original 14 resorts (but not with Riviera or future resorts, unfortunately). August is probably the easiest season to switch at 7 months to other resorts.