Southernstar... wow great summary and analysis!
I can buy the multiple failure mode theory. Seal failure leads to a lack of lubrication. A lack of lubrication leads to increased heat, pitting, wear, failure. How much surface area you have affects how quickly you realize failure - single row bearing thus will fail quicker than a double row, etc. The argument back and forth about whether it is a bearing load failure or a lubrication failure sounds a lot like the argument about which came first, the chicken or the egg. I looked at LN's website and see that they recognize the lubrication issue certainly as a contributor. It does seem then like the best solution would be the biggest, strongest bearing that you can fit with good (DOF) lubrication.
Personally, I understand the bearing weakness argument, but I just don't buy it. It seems to me that a steel bearing with proper lubrication should last just fine. That's my opinion and I think that's what I'm going to do with my car - steel bearing, outside seal removed, DOF. Will I still change the bearing with clutch changes? Honestly, yes I probably will, but mostly because it's just cheap insurance for me personally. I do my own work, so the extra labor cost is zero and the time won't be bad. I also buy a LOT of bearings at my work and can get the steel bearing for the same cost as a good lunch.
I'm not really concerned about oil getting into the shaft. Most people removing their IMSB have found oil in the shaft. It happens. It doesn't seem to be an issue. With the DOF at least that oil would not be stagnant.
I'm not really concerned about aeration either. If you look at the videos and good pictures of where the IMSB is installed you'll understand that it is a very, very tight place. That's why I don't like the splash lubrication approach... I don't really see a good path for oil to get into the bearing. Sure, maybe while the car is sitting and oil has drained back and filled the sump. But with the car running, oil pumping sloshing and moving about, I don't see a consistent, reliable way for oil to lubricate the IMSB. That's why LN uses a high wear bearing. The beauty of DOF is that it takes a lot of variables in lubrication out by providing a consistent flow. But you're pumping this oil into a very tight space. What's going to happen? The void is going to fill with oil, you'll probably even get some backpressure in the oil hose, and the excess will seep out of the small gap between the shaft and case. How is a lot of air even going to get in there? The bearing will be flooded and it should be happy.... then I'm happy.
Kirk