It's a matter of preference. Memory foam wrist rests are more common—they offer soft padding that contours somewhat to the shape of your wrist, but they may stay more flattened over time. Gel wrist rests are squishy, bounce back to shape quickly, and help keep your hands cool. Some users don't like the plastic surfaces they usually come with, though, and sharp objects may puncture and compromise the gel. If these common types don't work for you, alternative materials like leather and wood are also available.