You'll hear various opinions, but if the truck spends time on the street a spool isn't a good idea. It's cheap, but it will always be locked, and will scrub the tires every time you turn and make driving a chore. Some aren't bothered by it, but it definitely reduces streetability.
The front axle I bought came with a Lock-Rite in it. It seems to work fine, although I would prefer an open front or selectable locker in snow. It locks up well and is not too noisy. A lunchbox style locker will be the cheapest and easiest to install option. I've also had good experiences with Detroits. The air lockers or e-lockers are the most expensive, but really give you the best of both worlds.