I was going to say the strength difference would be very, very small if you did the calculations. The magazine said 5% which is basically nothing, and if you did the statistical analysis on their test that is probably less than the variability (meaning that the one test said 5% less strength, but they repeated the test is may actually say they were stronger...basically the test they did is just not that accurate).
I have greasables in the axle shafts of my D60, and solids in the driveshaft. The K5 rarely gets driven unless it's a trail drive and here in the Midwest there is always a water hole, stream, or mud we deal with. The driveshafts joints have been installed for a few years now and I just recently pulled the caps off the axle end while I had the shaft out....the factory grease was a little darker but that was it. The front shaft u-joints have been installed for probably 7-8 years now and have been removed from a couple of different times when the shafts broke and then re-used...still can't pull the caps off by hand the seals are so tight and never any sign of dirt or water in them.