Upgrading my M5

I never had the M5, but do have the M, M6, and M6II, so I can speak to the upgrade from the M6 to M6II. The IQ and AF on the M6 are similar to the M5. It's the same sensor, and the AF might be slightly upgraded on the M6 (released a bit after the M5). Everything about the M6II is better than the M6, and in some cases significantly better. The sensor is better, especially at high ISO. The AF is hugely better. The eye AF is a joy to use, and the tracking is excellent. You also get 14fps, which is amazing. It's a much snappier camera to operate. I think you will see it as a big upgrade from the M5. If you are used to having a built-in EVF, it might take a bit of getting used to. I actually prefer having the option of not having the EVF mounted at all. I only use it with longer lenses, so most of my shooting is done with fast primes, using just the LCD. I find it makes for better framing. It's also easier to get candid shots of people, because you don't have to have the camera up to your eye. I find that people will act much more naturally, even if they know I'm taking pictures, if the camera isn't held up in front of my face. Of course you can shoot like this with a camera with built-in EVF too, but it comes more naturally when you don't have the option of looking through the EVF. The detachable EVF is so small and light that you can always have it with you, even if you're not likely to mount it.