On our safari in the Masai Mara at the turn of the year 2018/2019, my Sony Alpha a7R III was able to prove itself in practice. In addition, I also had the new Sigma 60-600mm f/4.5-6.3 DG OS HSM Sport with me. I used it exclusively on the Sony a7R III during the trip on the Sigma MC-11 adapter. On the Canon 5Ds R, which was also with me, I mostly used the 400mm f/2.8L IS II USM with or without the 1.4 or 2.0 extenders.
Of a total of about 10,000 shots I took about one half each with the Sony and the Canon. A report and the pictures will be online soon, at the moment I’m still working on the pictures. Here are just a few remarks about the use of the Sony.

Nevertheless, the pictures with the 10x zoom are surprisingly good. A plus point of the Sony system is the ability to release the shutter completely quiet and the continuous shooting speed of up to 10 frames per second. Due to the tiltable monitor, I was able to take many pictures from a deeper perspective this time - this often looks much better. As a committed viewfinder photographer up to now, always looking down at people who carried their camera on their outstretched arm with a view to the small monitor in front of them, an amazing experience.
I also had the Sony G 24-105 f/4 with me - it has an excellent image quality up to the edges and is clearly superior to the Canon 24-105 USM II in my opinion. The meanwhile released Sony GM 400 2.8 is optically equivalent to the Canon IS III and even €1.000,- cheaper in RRP. In the meantime Canon has released two mirrorless system cameras in full format (EOS R and RP), which I consider very disappointing compared to the Sony cameras. If I were to start a new system right now, it would probably be a Sony system.