My view on autofocus is simply 'Does it do the job that I want it to?'. I'm not concerned that there might be a slightly better system on a slightly newer or more expensive model. I too came from a 7D and 400/5.6, moving on to a 7D II on the day it was released in late 2014 in the hope that its alleged improved low light performance would get me better shots in the gloom of early morning forests on an upcoming first trip to India. It was an improvement, but marginal. Anything over 1SO 800 or 1250 was as noisy as a rock concert. In 2015 I moved on from the 400 to the new Sigma 150-600 Sport and hefted its weight around with relative ease, taking shots as well as I could of birds in flight on my trips to the raptor migration in Spain as well as our local seabirds, including the terns at Long Nanny. Thousands of shots for dozens of keepers. It was hard work.
When the R5 arrived in 2020 it was time to leave my 7D II in the cupboard for a well-earned retirement and I was blown away immediately by the autofocus and eye detection, particularly when I bought an RF100-500 six months later, which consigned my Sigma to its retirement plan. Its high ISO performance in low light is stunning too. ISO 5000 or 6400 are easily usable and I've gone much higher when the situation warranted. I did consider the R6 at the time, but my need to often crop hard for flight shots in particular meant that the 45MP of the R5 was the game-changer against the 20MP of the R6. Even cropped at 1.6 times in body the R5 still turns out a 17.5MP image, not far off the starting point of a 7D, with the added benefit of actually being in focus. The R5 served me well and I loved it, I still do, even if the eye detection would sometimes latch on to buds or twigs instead of a warbler's eye in a bush. I soon learned to get around this by using my first choice back button for eye detect and a second for spot focus as a back-up. A trip to Spain for the spring migration in 2022 after Covid problems eased gave me many hundreds of keepers of birds in flight, rather than the dozens of the 7D II. I still felt short on reach, though and when I saw the specs on the crop sensor R7 when it was announced, especially the price point, I ordered one there and then.
It took 3 months to arrive - just in time for my upcoming autumn trip to Spain for migration at the end of August and I was bursting at the seams to give it a run-out. Unfortunately a health problem in the form of a stroke - thankfully mild - just a week later meant the trip the following week had to be called off. In the months since I've almost completely recovered and in March and May I got away to give my R7 a couple of run-outs in Fuerteventura and Tarifa. It performed well on both occasions. Its 32.5 MP sensor is very cropable, being the equivalent of something like 82MP on a full frame. I do try to avoid full Electonic Shutter, because it can give pronounced rolling shutter problems much worse than the R5, although it has its place in chosen circumstances. My preferred option is Electronic First Curtain, with its 15fps and no rolling shutter at all.
I still use my R5 for everything else, landscapes, night shots, people, family, steam trains, aircraft etc, but for birds it's been the R7 almost every time.
