I've ran a Lock-Right for probably 12 years or more now on 38's and then 39.5's and have broken a couple of the factory 30-spline stubs. Granted I don't have a ton of power and have an automatic transmission. It works great.
I know two different guys that have broken a front Lock-right in a D60. Both were full-size trucks (one Ford, one Chevy) with 42's, moderately built big-blocks, and heavy right foot. Both of them switched to a Detroit and have ran for many years with no issues. Haven't seen the Chevy guy for many years but the Ford guy has put the truck through serious abuse with no issues. As mentioned above all of the Detroit locker failures I have heard about revolved around something else breaking first. Breaking an axle shaft, especially an aftermarket stronger version, will put a shock wave back through the locker. I do know a Toyota guy who broke the front Detroit after taking out a chromo axle shaft.
For steering with a front locker I think any of them will tend to make a rig plow straight ahead. It's not whether you can physically turn the tires side to side or not but with them locked together they want to slide forward.