Well I guess I should toss my 2 cents worth. Started with a non c clip 35. Wheeled it open for 3 years just fine, and ALOT of nasty stupid wot action trying to break it. Was on 31s and it held. Locked it with a Aussie, broke it 3rd wheeling trip out...I knew it was coming. Sold it.
Picked up a 27spline c8.25. Sold it before I ever swapped it.
Picked up a 29 spline from a junkyard, grabbed a spare set of 29spline shafts as well and thicker shafts than the 27spline. It was sold because I got a d44 on trade around the same time.
Picked up a xj d44 on trade, cleaned it up, threw in an Aussie and planned to run it. These have 1/4" thick tubes, 2.65" diameter, tons of aftermarket. Great great axle! I had 120 into it for the locker and some paint. I got offered 700 and it left my life.
I now have a 8.8 that's being built currently. My xj has sat motor & axle less for 2 months so I wasn't in a rush to find the right axle lol. The 8.8 is great, strongest of all the listed. Ill be running 33x10.5s and am confident I won't be breaking my 8.8. However if i was in a rush the 29 spline c8.25 would of been kept(reason at bottom), since i had time to play i did the 8.8. The 8.8 is ALOT of work, the nice thing is you get it setup correctly for pinion angle and such so no shims. Anti wrap perches were nice since I have a 5speed. Nicer shock mounts. After thinking on it now for 2 months I wish Kept my c8.25..
We welded the tubes, have a truss, disks and stronger e brakes. My 8.8 was a lucky junkyard find, out of a 93 Navajo(explorer). It has a oru cast iron diff cover and an Aussie and 1, yes 1 chromo shaft lol. I just went to pull the cover, not the axle because it was drum brakes. Ended up keeping it after seeing the locker behind the cover. I picked up a new set of chromos for it, and now have a spare long side(passenger side). It's getting a complete rebuild & disk swap.
My honest opinion comes in here..for my personal useage, i disk like the 44 or 8.8 because both axle shafts are different lengths. Passengers always longer. If I had to. Close, I would do the 8.8 because spare shafts are far more plentiful at yards. The c8.25 I like because both shafts are identical in length so you only really need 1 spare. I use my xj as an "expedition or overlanding" type rig so carrying only 1 spare vs 2 is nice. Unfortunely I didn't realize this till afterwards.
The 29 spline c8.25 with chromos and disk would of been cheaper than my 8.8 in all reality and it would hold 35s im sure. And a c clip can also be limped off a trail with disks. Sure it puts ALOT of load on just a few bolts but it can and has need done!
The 44 seems to be the holy grail but because how I use my xj I think more out of the box..breaking a 44 shaft can be problematic unless you have spares. You probably won't find a spare shaft in a junkyard and if there's only 1 yard close to you..well then you SOL...and if your hundreds of miles from home this can really suck! While a c8.25 axle, you can get a spare shaft out of most any yard & again you only need 1. There's 4 29 spline c8.25s axles in 1 of my 3 local yards. The other 2 I don't visit so idk what they have. The 8.8 is also much more plentiful, so getting a spare shaft in a pinch will also be easier than a 44 which is why I ended up with it.
If you can pick up a d44 for only 250 complete, I would use it, or flip it for a couple hundred in profit. Guess it depends on your use & opinion though. Ill be running my 8.8 since I've got money into it. But if I could go back. 2 months I would of kept my 29 spline and built it up a bit because it would of been quicker & cheaper. The 8.8 is plentiful for spare shafts in a pinch and stronger than any axle in my post, hence the reason I finally ended on it.
I wouldn't run a 44 for my reasons posted..everyone wants them, so I personally would grab it, clean it up and make sure its all good and flip it for 500 or so. Then grab a 8.8 if you have some time or a 29spline if your in a pinch. My personal opinion.