If you are avid cooks, sheet glass, stainless steel or sealed slab granite are easiest to clean because there are no grout lines. That being said, the aesthetic of those materials don't suit everyone's taste. The next best alternative might be a glazed subway tile or glass tile with a darker grout line. I would hesitate to use any backsplash that had a rough texture to trap the inevitable grease splatter or bubbling tomato sauce.