If you choose leather, and there is a lot of Sun, a protected leather (which more or less has a painted surface will hold up best) but this leather is less attractive than a full aniline dyed leather (a more natural leather), the protected leather is also hotter in summer an colder and winter.

The leather used in cars is generally protected as any other type of leather would soon deteriorate. Have you ever been in Dallas and got into your car on a very hot day you can't even touch the steering wheel. A protected leather is just about the only leather that would hold up.

On the fabric side the best fabric that holds up to direct sunlight is the "Sunbrella" type of fabric (there are several companies that make this type of fabric).

Another option is to go with white so that fading is not an issue.

Also remember that its the UV light from the sun that can be damaging. In cars the glass stops most of the UV but everyday household windows are not designed to stop the UV light.

If you choose to use leather there are leather conditioners with UV protection that you can apply once a year which will help with sun protection.

Karen, Guardsman, Guardian, and Leather Master to name a few would carry leather conditioners with UV protection.