The rear bearing is the typical failure, but the heat from that failure can wipe out the electronics at times too.
I don't think the typical 105 or 140 amp alternators are any different from each other in longevity, but the 140 will hold up better in the SSEi'*, or other models running large amps and demanding audio components.
sells beefed up units. Beefed up electronics, and a better design for the bearings. We're running about a dozen of these here, and they all seem to be holding up fine. Some of them after about 2 years.
I'm running one of the 160 amp units. Started life as a 140, beefed up to 160 with better bearings.