I dont have a locker (wish i did) but... from reading other posts i should be able to help you out a little.
O.K. First we need to know what you are using this rig for. Is it going to be something like 70/03 on road to off? or are you planning on 50/50? a full time trail rig? If you aren't goin to spend a whole lot of time off road, and have the extra money you should go with a selectable locker like ARB, that way you can engage/disengage your locker whenever you want. If you are goin to be off road a lot you could go with an automatic locker, like detroit, these are engaged all the time but when turning they ratchet to minimize tire wear. And if you are really tight on money some people put spools in their rigs. Just because these are cheaper doesnt mean that they are any less effective, they are just locked all the time, kinda like a welded diff. I have heard that spools are not as safe onroad but that battle never seems to end.
Hope that helped