I had an EZ locker in my d35 and hated it. From what I've read, ppl with manual trans don't like them, ppl with auto's don't mind them. My current combo is 8.8 rear with factory Trash-Lock and front Aussie. I've got a disco axle so I don't even notice the Aussie on the road. This setup works rather well, however I'm planning on going with a No-Slip in the 8.8 when/if I do a gear change.
So... my opinion is this, if you have an auto with open diffs f/r, then go with a lunchbox locker in the rear first.
If you have a manual with open f/r, spend a little more and get a No-slip or a real locker like a Detroit.
If you have a rear LS, then go with a front locker first.
You may want to state what your current combo is as far as trans, axles, TAD's. Otherwise we can only make educated assumptions as to what you have.
Also, like others, I'm not a big fan of welded diffs. Not saying I'm totally against them, just not a big fan.
Dale