I think everyone is right here. It's just their opinion. I have 4 new Sterns since cabinet splitting has been reported. I, luckily, have not had the issue on any of them.
I picked up the brackets and the screws from Amazon. I intend to do all 4 corners, but I can see that the front would be the most obvious ones to do, especially because these will show the cosmetic defect immediately. So for sure, do the front 2 corners.
I liken it to putting Cliffy's on a game. Games never had them and survived without them. I put Cliffy's on all my games to prevent an issue instead of waiting for one. And Cliffy's, as well as the better leg brackets, are a small price in comparison to the cost of the machine.
I picked up a refurbished Monster Bash a few years back and I will say I was very happy to see the better leg brackets on all four inner corners. Just showed attention to detail... In addition to the potential splitting, the better bracket should prevent a "pull-through" which I tend to do when installing and over-tightening the leg bolts. The old style bracket was pulled right into the 45 degree wood corner spline. Did that on my Batman Forever... not fun. That whole widebody was a little wobbly. I'm in the process of re-doing that cabinet and will be installing the better bracket on all corners.