The standard chain is a 525 size. When I replaced mine recently I went to a company close to me that makes custom sprockets. Apart from getting case hardened sprockets that will last longer, and an 18 tooth front, I also got them made slightly thicker to take a 530 chain. This has links that are the same length but are thicker, and is designed for heavier, larger bikes. Consquently for not much more money you get a chain that will last significantly longer, assuming it's lubed as frequently as it needs.
Matt
