If you check out the DVC part of the fixed info on
http://wdwinfo.com you'll find some discriptions and photos of the DVC units. Here's a link for Beach club, you can rummage around from there.
http://www.wdwinfo.com/dvc/bcvillas/room.html#rooms
You're not missing anything , the DVC rooms offer reasonable value over two regular rooms but not many people look at them as an option. If you do want to look at DVC units you could save some $$$ by renting points from a DVC member and letting them make the booking. I believe a lot of the "risk" of this venture can be covered by using paypal so it's not just a case of sending someone a cheque and they do a runner. Depending on the number of days you want and if you can avoid weekends you should be able to get the rental for less than $400 a night, maybe as low as $300 depending on the season.
A studio is basically a standard hotel room, at BCV and BW they offer a queen sized bed and a double sized sofabed.
A one bedroom has a large main bedroom with a king size bed, immediately off the bedroom is a jacuzzi, and a sink this leads through to the bathroom which has a walk in shower ( but no bath as it's in the other room). The living room has a sofa bed, there is a full kitchen and a dining area as well as a breakfast bar. You also get a washer/dryer in the room
A 2 bedroom is the studio and one bedroom attatched together, sometimes they are a "lock off" so the adjoining door can be locked from either side and the studio has a seperate entrance.
5 is a really difficult (read costly) number to accomodate, depending on the age breakdown of all concerned, you could consider a two bedroom at OKW it would be cheaper ( both in $$ through CR and renting points) the units are considerably larger and the 2nd bedroom has two queen sized beds in it so it may avoid anyone having to sleep on a sofa bed. .