I transitioned from the a6000 directly to the a7rIIIa. Huge difference. Of course these cameras have a lot of years of separation which equates to numerous technology improvements. I love my a6000. I LOVE it. As an APSC it is rock solid if a little primitive. I used it with a lot of vintage manual focus lenses and a couple cheaper AF lenses. But I had reached the limit with that camera regarding image quality. I borrowed some Sony G lenses from my brother to use on the a6000. While yes, better glass makes the most out of the camera, it is still somewhat equivalent to putting a Ferrari engine in a Corolla. It does improve things quite a bit. But that sensor is still APSC and the AF tech is very old school. I upgraded to the a7rIIIa and it changed my life. You can crop the heck out of an image and get super sharp images with vastly improved dynamic range. It still works with my vintage lenses since they were designed for old 35mm film cameras. It even shoots in APSC mode for my APSC AF lenses and does a better job as an APSC camera than the a6000. The downside is the new lens price for full frame Sony cameras is absurd... Unless you go with non-Sony brands. Then it is quite reasonable. My favorite AF lens is the Yongnuo YN85, a fast portrait lens. It came in under $300. An equivalent Sony lens would be three times the price. The biggest difference is the megapixels and AF tech. Grabbing the eye of a bird in crisp focus automatically is ridiculously cool, something the a6000 could never do. And I went from not using the viewfinder at all on the a6000 to using it a LOT on the a7rIIIa because it is SO much better. So comparing these cameras is really a history of Sony camera evolution. And as you should expect, the newer camera is ridiculously better in every conceivable way. Just stay away from the Sony lenses and you won't go broke. There are plenty of non-Sony lenses that perform admirably.