I'm only guessing, but probably because most lenses used on an R6 have an AF/MF switch. The RF-S lenses so far don't have a switch, and you'd have to change AF/MF in the camera menu.I wonder why they didn't include the AF/MF switch on the front of the body like on the R10/R7? I think the R6 market would want that feature and I think all future models should have it.
Canon also says the R6 Mark II has a resolution performance that is superior to the EOS 5D Mark IV, which provides 30.4 megapixels.
In theory, it would be great for any subject that isn't currently moving but could start moving. In practice, I found that I was far better than the camera at deciding when a subject was moving vs. sitting still, so I never used AI Focus on cameras with that as an option. It was not an option on the 1D X and is not an option on the R3, which is a contextual message about how Canon views it's utility.What are the scenarios for which this mode is better than the other two?
The cost isn't what you pay, but what you pay minus what you eventually sell for. I usually buy my Canon gear mint used and sell it near-mint used. The actual cost of the Samyang and the Canon might be very close.135L is pretty much DOA here in Australia since it’s $3899 AUD and the 135GM is only $2300 AUD. Not to mention you got the option of the Samyang 135mm f/1.8 AF for around $1400 AUD.