I prefer a tiled shower. For a bench if you are using a receptor that won't be tiled, to keep things from leaking, I suggest you look at Better Bench at www.innoviscorp.com. They come in various sizes and styles.
For much less money, a qualified tiler can make you a tiled shower. For some additional help and ideas, check out www.johnbridge.com.
Another suggestion is http://www.schluter.com/143.aspx. This makes a bulletproof tiled shower. You can use one of the kits, or make a custom sized shower.
I've used both of those products, and found them to be top quality. I used their tub conversion sized kit (Schluter) and the large corner Better bench in a shower I built for my mother.