[davidmanze]

I place a certain amount of respect for Sony's latest E mount lenses for sure ...... I also place high expectations from a pro 600mm F4 OSS Sony lens ......

........ does that sound so strange ?? Given the performance of their recent glass.

No, I'm basing this on the Sony A9 in it's latest FW stance and having the appropriate level of tele glass to put an end that too short a reach issue ...... (that's where I live ...... at 600mm APSc)
Addressing the lenses themselves ....... firstly construction ...... without metallurgy analysis of the body, it sure looks superbly built, how much metal remains to be seen .... with sealing and internal focus and internal zooming ( focus breathing? to be seen) ...... with rapid and accurate focussing on both models (best on the 600mm F4 of course)

Sharpness awaits a technical review for the numbers ....... but DPreviews's review seem to confirm any doubts you have raised You2!

With Sony being the best selling ML this is huge ...... and I don't apologize for enthusing at all !!


DPreview's review:

https://www.youtube.com/watch?v=9BZBZFWtF_0

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As if a D500 / D850 would give you 7 or 10 frames per second in perfect focus . Sorry Dave, but that's definitely not happening in my experience, and that goes for the Tamron, the Sigma and for the Nikkor 300/4 (with active VR) as well. Especially the engaged VR will throw your focus point often off target.

The Z 6 should be a bit faster in aquiring focus, but the Z 7 is nothing to write home about in terms of speed - and it is not meant to be a speed-giant anyway. But if I manage to engage tracking (in my eyes far too complicated compared to the simple 3D-tracking), this tracking will cover the whole frame - of a full frame, not your tiny D500  .

And then, α9 and X-T3 are at least 3rd generation bodies. I can't speak about X-T1 or X-T3, but X-T2 needed 4 major firmware upgrades during 2 years to get to a usable AF-C - which still lacks a feature I often need: Manual override, when the bird sits behind twigs or hidden behind reeds is impossible with an X-T2, and the reach of the 100-400 sucks as much as the focvus limiter or the wrong places manual focus ring.

So, in ML land the α9 rules. For now... But both Chris and Barney had a hard time in a low lit soccer arena. The fact the 200-600 doesn't extend is something very welcome.

Btw. the 60-600 is better than the 150-600 sports at the long end, and less poorly balanced, too, as the extension tube is made of plastic and the hood as well, so much lighter than it's heavy metal brother.

     
   Just to say first I'm looking from a birders viewpoint  ...... that means primarily speed of AF, reach, IQ and focus .... in many ways I wish I wasn't ...... but there it is!
 No, I don't get 10/10 shots in focus with BIF either ....... I get three or four in difficult BIF situations up to 8 when birds are relatively still.
  You saw Chris and Barney struggling ??  ..... I must have missed it!

   Any way this about Sony and it's great A9 ..... and the lenses you can out on it ........

  and to trump it all ...... it's the Same price as the top Sigmas ......

 Which would you choose if you had an A9 ..... the Sigmas?