I have no personal experience with a locker, but basically if you do any street driving, a locker would be a good idea. However, I'm sure a couple of people do use a spool on the street on a limited basis. But it would be suicide in the rain.

If it is strip only, I can't think of any reason why you should not go with a spool. I'm sure a spool is more durable than any locker, less expensive and why carry the weight? And with a Dana 60 spool, you can upgrade to 40 spline axles for extra long-term insurance. Not sure if a locker would have that option.