I'm a new
DVC owner and I haven't actually stayed in a villa yet (studio or otherwise). I have studied the floorplans and looked at lots of photos of all of the DVC resorts and here are what I believe are some of the significant differences. I'm using the rooms at YC and AKL as a comparison.
A deluxe room at YC/AKL will have either 2 queen beds with a nightstand in between or a king bed with nightstands on either side. Other than at OKW, a DVC studio will have 1 queen bed with one nightstand only and a full-size pullout sofa. Comfort level of the pull-out sofas has been debated here quite a bit. The newer style sofas used in SSR are apparently quite comfortable for sleeping. The older style (found at BCV and BWV) are not very comfortable for sleeping, but rumor has it they are being/will be replaced over time with the newer, more comfortable style. I don't know whether VWL, VB and HHI have the older style or newer style sofa beds. OKW's studios have 2 queen beds and no sofa.
A deluxe room's bathroom vanity has 2 sinks. A studio's vanity has 1 sink.
A deluxe room has a mini fridge. A studio has a kitchenette with a mini fridge, microwave, toaster and small sink.
Other furnishings in the room appear to be comparable: an armoire holding a TV and some storage drawers, a small table and 2 chairs. YC's rooms have a dresser (AKL's rooms do not) and the studios do not.
I don't know how the rooms compare in size, but I'm guessing they are comparable.
In my opinion, a DVC studio falls just below a deluxe room in terms of comfort level -- DH and I prefer a king bed with two nightstands and appreciate having two bathroom sinks. However, even though I bought in recently and paid a lot for my points, my cost of staying in a studio is about 1/3 the cost of a water-view room at YC, so I'm more than willing to downsize to a queen bed and 1 sink! And having just the one queen bed plus a sofa in the studio should make the room feel more spacious. Of course if you want two beds, there is always the option of booking a studio at OKW.
If you want to see for yourself what the studios look like, there are several web sites that have photos of the rooms. If you go to
www.disneyvacationclub.com they have 360-degree views of all of the DVC rooms and also the floorplans. There are also photos of DVC villas at
www.allearsnet.com.
Hope this helps!