And I'd argue Dolphin has better beds, toiletries, service, food choices, and LOCATION. It's hard for me to come up with any way DVC's "quality" is better than Marriott. Sure, shiny new RIV has nice tile, but there are plenty of very, very tired DVC properties. Oh, and you don't have to be locked into a timeshare for 47 years. It depends on what OP values.
OP sounds like they are on the fence. I think it's important to know the other options, and I think locking into this incredibly complicated system is not for everyone, even if RIV has nice tile. DVC itself is a complicated product with a lot of rules, and a lot of properties that aren't at Dolphin level. WDW is complicated also. It's a lot.