It all depends who you speak to. I had one andit was great but other people had them and they failed. The simple fact is that it really matters on how well they're installed I think. Some diffs have very little room inside to route the air line and it's easy to snick it on the ring gear. In terms of strength, the carrier is much stronger and has less flex. Maybe they have improved the air line set up. I don't know. But certainly I wouldn't doubt the big metal bits.
If your diffs are all good and quiet but you want your lockers at 100% then I'd just bite the bullet and for the price of one ARB in a box, I'd fit two new locker motors. You'd be set for years then with no reliability issues. Remember that fitting ARBs means both diffs out on the bench with complete disassembly.
Karl on here will have themmy diffs are good Chris,who sells 'new locker motors' in the UK?
cheers