thats a question many people have different views on, my view is locker in the rear if only one locker but that's me. A locker in the front can cause some nasty affects while turning ,I dont know what you have for a vehicle be it CJ,YJ,TJ etc, anyways if you dont have locking hubs I wouldn't put a locker in the front at all unless adding locking hubs, so you can unlock and free spin the wheels or you will have really bad maner steering on roads.Unless you install a locker that can be locked or free like a ARB air locker, or the OX Tracs locker.They are spendy, think around 600 or so for either of them. Im in most cases simple is better, so I like detroits not much to go wrong the ARB alot of things can go wrong, the Ox Tracs lockers look cool but in the front the cable sticks out the front as someone pointed out to me so could take a hit. Also another thing to concider is if your going forward weight shift rearward so front wheels dont get as much traction as rear in most cases, some yes front has more, this is where people make there decision etc.
Jeep what else matters.