Hi Elizabeth,
You are considering two of my favorite resorts at Walt Disney World!
Disney's Beach Club Resort has a beach-like, New England feel, and
Disney's Old Key West Resort has a Florida Keys vibe.
Disney's Beach Club Resort offers traditional hotel rooms. Both
Disney's Beach Club Villas, the villa side of Disney's Beach Club Resort, and Disney's Old Key West Resort, are deluxe villa resorts. They offer not only deluxe studios, but also one-bedroom and larger villas that offer a kitchen and washer and dryer right in the villa. Overall, you will find that the villas at Disney's Old Key West tend to be more spacious; however, those at Disney's Beach Club Villas certainly have ample space.
Also consider the location of each of the resorts. Disney's Old Key West Resort is a bit more secluded, and offers boat transportation to Disney Springs, and bus transportation to other locations throughout Walt Disney World. Disney's Beach Club Resort and Villas are close enough to Epcot and Disney's Hollywood Studios that you can take a boat or walk. All other transportation is by bus. I love the location of Disney's Beach Club Resort and Villas. Not only can I walk to my favorite Disney theme park, Epcot, but the location on Crescent Lake means that you are walking distance to numerous other resorts as well as all of the fun along
Disney's BoardWalk.
For a side-by-side comparison of these resorts, check out the
Walt Disney World resort comparison tool. I have stayed at each of these resorts and happily would stay at each again!