RF 800mm and 1200mm lenses, do they make sense?

[Fast Glass]

The 800mm doesn't make a lot of sense to own in my honest opinion. It is much more expensive than a 600mm f/4 and extender and less sharp. If you compare it to the EF 800mm f/5.6, the EF version is significantly sharper. It is less modern, yes. But at the large price spread and lesser IQ. How much good is it? Up to you to decide, I don't see the value in it personally when the RF 600 exists for thousands less and better or the EF 800mm as an options as well.

The 1200mm while ridiculously priced, at least does something slightly better than the RF 600mm f/4 based on the MTF charts. But not better than the EF 800mm f/5.6. So is it really worth the 18k price point and significant IQ shortcomings? Again it is up to you, but I don't feel like it is. Even if you wanted the build of the more modern lenses the IQ difference is not huge compared to the RF 600 and the cost savings are dramatic.

I think if Canon really wanted to dress up an existing lens, do that with the outgoing EF 800mm f/5.6. Give us some updated optics, update the build and wiring to the more modern RF mount and boom! You have a lens that justifies the price tag. Because it has to have costed something to revise the optics of the RF 800mm and 1200mm and make a new lens barrel even with all it's shared components. I think the funds were far better off being invested in updating the EF 800. Even if it costed more, you had a standalone optical design that would sell much better. Because it offers you something you can't get by simply adding and extender on a already existing lens.

This is my thoughts after reading Bryans excellent reviews (As always) and his extremely useful ISO charts. But I'm of the opinion, even if I was willing to spend the money that I wouldn't because there are options that have better IQ. Even with all their caveats.'

It's kinda a long rant of a post, but these are just my feelings on it. I wouldn't step on anyone's toes if they bought them and I wish anyone who owns one all the best.