I run a mini-spool in my 91WT SWB Sierra. I am a fan of this setup if you cant afford an Air Locker. I recommend a mini-spool over welded from a reliability (less likely to go bang) point of view (On road/Off road performance is the same either way).
I have been running my spool for a year now and my tyre wear is minimal at the most. I run 31" Maxxis Bighorns on 15x8 rims, and you would struggle to tell the difference between the front and rear tread wear. It has done a few thousand road KM's with the spool.
I agree 100% with Gwagensteve's comments.
Having said all that, I think I have broken a rear axle while out playing last weekend. Its quite strange (scary) how the car behaves on the highway with "one wheel drive". It was a slow trip home...

Its not super common to snap rear axles, its just my bad luck I think! haha
I'm looking forward to being covered in diff oil and grease once again!
If anyone in Melb (SE Suburbs preferred) has some spare rear axles then please PM me!
Cheers all,
Pez