the cost thing is important,
So you're the average Zooker, eh?
yes, they do cost a lot more. But set up is actually easier than most think. With a lunchbox locker, you remove the carrier, pull off the ring gear, open the carrier, remove parts, flip sidegears (if they aren't too worn, and in most of the 20+ year old rigs, they are) or replace them, check play with feeler gauges (not all that easy) and set it back up. Then hope the axle tube isn't tweaked in the least bit or the locker won't work properly.
For the ARB, you remove the carrier, peel off the ring gear, bolt the gear onto the new ARB carrier, drill and tap a hole for the air fitting in the diff housing, attach fittings, set it back up, then plump the air lines to the pump. installing the pump and ait lines took me longer than setting up the ARB. It's more tedious and time-consuming than anything.
The greatest advantage is the ARB is no compromise. It's completely transparent when its off, which means it's invisible on the road (something no lunchbox can claim, regardless of how well it's set up), and it's full locked when you need it, all at the flip of a switch. You'll be hard pressed to find many ARB users (or any selectable locker for that matter) that HATE their lockers. Not the same for spools and lunchboxes.
But money is money, and for the fishing truck, spending near a grand to lock up the rear is way pricey. So install a lunchbox, and if it does the trick, right on. If you find it's not what you want (mainly on the road), you can always ditch it in favor of an LSD or an ARB.
Personally, I don't recommend automatic lockers to anyone anymore. Just too many damn hassles and I don't like them on the road.