It's better to have the pickup wider than the strings, than the other way around! That way the pickup won't "miss" anything by being too narrow. That being said, the difference is subtle at best. I wouldn't worry too much about it, I actually ordered a brand new set of Rebel Yells with 53mm spaced bridge, and then figured that 50mm would perhaps be closer. But I didn't worry about it, because it sounded great and like I said wider is better than narrower!
