stock fj40 axels have the same thickness as dana 60's. If i remember right the width of an fj40 axel shat is 33 mm while the 80 i think is 28. so the fj40 may be a better choice. Mine have never broken
You should have asked this in chit-chat because many posters do not cross forum sections. Your answers will definately coincide with whichever forum section you are in for the most part.
I own an 80, so of course the 80 axle is stronger in my opinion. My conclusion is not based on the actual knowledge I have of the parts within, but instead what I have heard, and of course the fact that I own an 80 series.