My 2 cents...
I do a fair bit of 4wding with Toyota's, Nissans and a hybrid Toyota with Nissan axles here in NZ. All are on 35" or 36" simex's and locked both ends. I have no axe to grind and all have pro's and cons. These are issues I have witnessed personally. As for me I run rover axles with a mixture of Ashcroft and Kam internals on a 3.9 megasquirt & EDIS 110. I have ditched the Salisbury and fitted a rover axle in back as well. Both diffs are locked and pegged but run factory crownwheels/pinions and 35" simex's. I have blown one diff and I blew 2 AEU2522 cvs and a locally made 4340 shortside front halfshaft before fitting Ashcroft's gear but all good since. I went this route as it allowed me to upgrade over a number of years as I could afford it and it didn't need certification (Engineer Certification required in NZ for major mods like axle swaps). I would be happy to put whatever gave me best bang for buck under my truck but this is what I have noticed.
80 series cruisers have a 9.5" rear diff and a high pinion (hypoid) 8" front.
The rear is very strong but I have seen a couple with factory 4.2 diesel motors shear all the studs off the drive flanges on the hub (as per previous poster) and a long side halfshaft with a twist in the splines bad enough to stop the sliding dog on the factory locker moving. Recently a club member's LS1 powered 80 lunched a rear diff towing his jet boat but may have been damaged during a pretty rough long weekend on the coast a week or so before. Factory lockers (front and rear) are operated by a small 12v motor with a worm and crescent gear. The motors are a bit of a weak link as they get water in them or the magnets (which are glued to the housing) fall off and stick to the armature. Vacuum, air and cable conversions have all been done to address this.
The front in stock form is a bit fragile in reverse. I have seen two 80s lunch front diffs when reversing from nose down in a ditch. It is common here to fit the 8" hi pinion diff head in the front of hilux's to improve front prop angle with big lifts.I have also seen a hilux do the same thing in reverse with an 8" hi pinion front diff. The pinion bearing preload is set using a crush tube and replacing this with a solid spacer seems to help but its a precision machining job. The axles and CVs seem pretty strong but have seen 2 blown CVs. Longfield CVs are available for them and take an incredible amount of abuse but worth noting that the "Longfields" that Trailgear now sell are not made in the same Factory (RCV - Rockford CV) that made them for Bobby Longfield before his death. You can however now buy direct from RCV which you could not while Bobby was alive. Also, the steering arms are bolted to the swivel housing on cruisers (not part of casting like rovers and Nissans) and these bolts can come loose if running big tyres. Marks adaptors in Oz does a one piece cast swivel housing to cure this. Different years got bigger brakes (as per previous poster) which don't allow 15" rims and also some have narrow drive flanges which can strip the splines but not sure of the years.
Nissan GQ's run 233mm diffs (9.17")
Rear - I've not seen one let go yet. Rear middle diff is wrong setup for landrover but seems very strong. Rear brake calliper design allows a badly worn pad to fall out followed by the piston if left unchecked! Factory rear locker is vacuum operated and actuator is reliable but have heard of people blowing the teeth of the locking dog (mates truck has ARB in rear now for this reason). Halfshafts are not floating like Rover and cruiser which I don't like as halfshaft directly supports and locates the wheel.
Front diffs seem equally strong but housing can bend by the swivel ball. Welding gussets in here seems to be the cure. Freewheeling hubs and hub gears seem to be a weak link. When these fail they can destroy the splines on the end of the CV. Have seen CVs fail but not commonly. Cool bits for Nissan axles are not as varied as Toyo because the USA never got the GQ patrol/safari but Nitro gear make shafts and CV's and I hear RCV do now as well.
Spares (stub axles, seals, bearings etc) are considerably dearer for Nissan or Toyota than Rover here. I bough a new stub axle complete with bronze bush and seal for my rover the other day and a mate with a Toyota commented that a stub axle for him would have been 2-3 times the price.