Come on neuro, that's comparing apricots with carrots.
The RF 100-400mm is a budget lens, not built to the same standard as an L version.
It's a cheap option but can in no way be compared with the very solid, optically superb Sony 200-600mm, or with the EF or RF 100-400mm.
Here are the current UK prices:
Sony 200-600mm - £1329 (including £100 cashback)
Canon 100-500mm - £2979 (no cashback available)
I've handled both of these lenses while on safari in Kenya a couple of weeks ago. Build quality looks about the same to me. Optically both are superb, I doubt if anyone could tell images from them apart. The Canon is lighter and can be fitted in a standard rucksack. The weight is pretty irrelevant of the lens is on a gimbal, or is being used on a beanbag in a vehicle. I had been thinking about getting the Canon 100-500mm to replace my EF100-400mmL, but if I wasn't already tied into the Canon system (2 bodies, 8 lenses, 3 flashguns), or if I has £10K going spare, a Sony a1 and 200-600mm would be extremely tempting.