Most of my issues have been with the ring and pinion, Being open or a sure grip won't change these failures. I did buy a car that needed a 7 1/4" replaced because the spider gears failed. I was too broke and busy to replace it so I welded the spider gears into a Lincoln locker. I put some bigger tires on it and broke both axle shafts a few days later when it wheel hopped racing a friend.
I normally use 8 3/4" diffs but I have tortured a few 8 1/4"s without breaking them. I had a '95 4.0 Cherokee that I swapped a Klune-V 2.7 under drive and a 3.8 Atlas transfer case into before swapping to front HP Dana 60 and a rear 14 bolt with 5.13 gears. It had an automatic with a 91 to 1 first gear ratio in compound low with the stock axles. That's over 22,000ft/lbs of torque to the wheels. I welded that 8 1/4" too and had 35"x12.50" tires. I was amazed it held up. In 2wd compound low it would overpower the rear brakes at idle and slowly hop the rear tires. Top speed in 1st gear was about 6mph too or 20ft per minute at idle in first gear. Top speed in compound low and OD was 17mph on the rev limiter. It was ridiculous.... After the diff swap compound low was 132 to 1. Talk about some wild torque multiplication.