The lower axle appears to be a newer aftermarket design. I know GKN/Lobro sold this kind of design and it was a quality product. They are functionally the same - the design is updated to allow taking the thing apart without having to cut off the old can and crimp on a new can.

So all other things being equal, the on the lower one you can replace a torn boot without special tools.

I'm kinda surprised to see one of those newer ones in reman circulation.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles