Your [sic] right, the 14-35 is not a true fish eye lense [sic], however at 14 mm it does give somewhat of a fish eye effect.
Well, with respect I beg to differ. I agree that it has ultra-zoom capabilities in common with the fisheye, although they tend to be much shorter FL still, but as you can see from the image of the coffin outer for the Ancient Egyptian Nakht, taken at very close quarters, it does not in any way render the curved lines of straight objects that are the hallmark of a fisheye - which is why a fisheye has that name, after all. 🙂 The rather ragged lines on the base are the actual wood may be due to its original natural shape, or warping over time.
As regards the two Sigmas:
They both work seamlessly with my R5, R6 and R6II bodies. That said, each lens has its own strength.
The 150-600c is much lighter, which can be convenient, especially as I shoot hand-held pretty much exclusively. With the R5 I can put that in 1.3 or 1.6 crop mode and shoot with a FoV equivalent to 195-780mm or 240- 960mm respectively. Even with the loss of pixels: 1.3 renders 26MP, while 1.6 gives 17MP - that is enough for my purposes, so I have no need to buy a separate crop sensor body, especially as I don't consider Canon have made a true replacement for the 7DII yet. The 150-600c is relatively cheap compared to many alternatives - for example you could likely get 2 or 3 for the cost of the RF 100-500L, although that is a superior optic IMHO.
The 60-600s is made to a higher grade. It is weather sealed, and weighs about 1kg more than the 150-600, which is OK for me, as I can handle it, but that could be significant to many. It is a one lens solution, so it would be perfect if one has the capacity to take it but wanted only the one lens, especially for trips involving international travel - e.g. on safari to the Masai Mara, or Antarctica.
