There are two main types of bed skirts: gathered, and tailored. The first uses a sewing technique to create a bouncy, full look with lots of fabric; the other takes into account the specific measurements of your bed to bring a straight, flat edge of the fabric and wrap it around the exterior of your bed frame.
Gathered bed skirts are often cheaper because tailored bed skirts are much more specific and require exact dimensions, instead of simply the size of a mattress.
Which would work best for you? That depends on the look you're going for. If you're looking for a sleek, modern, minimalist appearance, then perhaps a tailored bed skirt will be your best bet.
For a more boho or romantic look, consider the gathered type of bed skirt. They can help a bed look fuller, more relaxed, and more comfortable - which is often exactly the type of feel you need in a bedroom anyway!