So a quick update to this thread too...
Having now got a genuine RC4WD Yota II front axle to replace the second broken Chinese eBay copy, I thought I'd do a quick side-by-side comparison for anyone who might be wondering what the actual differences are:
photo. RC4WD Yota II axle in the foreground.
As you can see above, superficially they are VERY similar - and indeed until I'd actually got an RC4WD version in my hands, I presumed they were made in the same factory, so close were they visually (on an eBay listing at least).
However, once you get them side by side there are some immediately obvious differences - not least that the eBay special comes complete with the 4-link brackets and a servo mount (plus the tie-rod and drag-link) in a plain cardboard box, for your $45 or thereabouts...
Conversely, the genuine RC4WD Yota II axle comes in some quality packaging - including a foam cut-out and branded plastic box, but is only the bare axle - the 4 link brackets and servo mount, and drag/tie rods being available for additional cost if required.
For my installation (on a leaf-sprung build with a Chassis Mounted Servo) these were unnecessary, and I already had my existing steering linkages of course.
In both instances, the part which broke on my previous axles was the cast end of axle casing inside the steering knuckle. What tended to happen was the dog-bone of the stub axle jammed in the cup and bent under extreme duress, and once the axle started turning again this in turn caused force on the two king-pin bolts, and in both instances, one or other of the cast tabs snapped off the main axle case - rendering the whole casing unrepairable and useless... (see the photos above from the RC4WD event for the most recent example).
As you can see above, the ends of the RC4WD axle casing (foreground) ends are much more substantial and almost completely encase the axle cup in comparison to the skinny tabs on the copy axle... hopefully this will prove much stronger and less likely to fracture in future.
The next obvious difference is in the quality of the supplied 12mm hexes:
The RC4WD (again foreground) axle having much better quality machined (in steel?) hexes - complete with locking set-screws.
As you can see, both axles have the same design steering knuckle (with tie-rod brackets fore and aft), and although visually and dimensionally almost exactly the same, the copy axles use what turns out to be a rather clumsy brass bush between the axle casing faces while the RC4WD axle is machined much closer, and the screws (which are also much better quality) thread directly into the axle casing.
It's worth noting that the copy steering knuckles can be used as replacements for the RC4WD ones (since there is more free play and the brash bushings used), while the RC4WD knuckles do not fit on the copy axles due to the tighter tolerance of the king-pin faces.
The differential housings are again very similar - the only real difference being the black (and again better quality) socket-head screws on the RC4WD version. As with the diff cover plate on the other side, I'm sure these components would be interchangeable if required.
Similarly, the inside of the differential looks very similar, as do the straight-cut crown and pinion gears:
As with my Chinese copy axles, I found the pinion gear shaft did need shimming slightly to stop any thrust play - although in comparison, the RC4WD shaft only needed a 0.1mm shim, rather than 0.2 or even 0.3 I've used on the previous copy axles.
And finally, another view of the more substantial axle casing ends - a quick visual inspection would suggest the axles themselves are made from better quality metal too.
Overall, the finish and quality of the RC4WD axle is just 'better'. You can tell it is the original, and the eBay special is the copy - a close copy dimensionally and visually, but with some detailing and build-quality issues. That said, the copy axles are still well finished for the price.
I hope that helps anyone who is looking to purchase these scale style axles for a build, and that, in my experience having snapped two of the cheaper eBay axle casings now, I would suggest it's worth paying the extra $20 or so for the proper RC4WD version - although it remains to be seen how much stronger it is actually likely to be.
note. as I understand it, ultimately is also a good idea to fit the XVD (CV) axle internals (rather than the standard open dog-bone style) to this axle, although those are a substantial $39.99 extra... although at least that ought to eliminate the dog-bone binding and twisting that the previous axles suffered from, while maintaining maximum scale looks.