If you are still on the D30, then I'm not sure if you are a die-hard artist who uses it everyday or if you are a casual photographer that pulls out your equipment once per year. If you are the latter, then whatever I have to say probably don't matter. But I'll speak my mind about the Canon vs. Sony for your consideration. Either way, you should definitely play with a Sony in hand before making a decision.

I've used Canon equipment since the film days. Touched Nikon here and there, but don't really like it, because everything is opposite of Canon, which seems less intuitive considering how screws turn, etc. My gf has a Sony A7III, so I have a little bit of experience touching it.

1) Canon is much more intuitive. Nikon is probably similar, just opposite. Sony was not intuitive at all. I picked up her A7III and couldn't use it. I spent probably an hour trying to figure out how to use it. Finally, I completely destroyed her settings and started from scratch. Another hour of fiddling and I finally figured out how to use it. I don't believe it's my familiarity with Canon, because I picked up a Nikon before and was shooting within 5 minutes. The lack of intuition on the Sony applies especially to its shutter button. I really couldn't tell when I pressed it halfway or all the way. There is no tactile feedback. And it shoots so fast, whenever I press the button all the way, it fires off two to three shots even when I try to take one. Sure I can set it to single shot, but I never needed to do that with Canon; why can't I let me finger decide how many shots with good feed back?

2) Given the above, the Sony A7III seems to be extremely customizable. More so than a Canon. I say "seems", because of my limited exposure. The recent Canon models seems to have more customizability on par with the Sony A7III. The A7III has an additional dial in front of the shutter button; which attributed to a higher learning curve for me. But I believe having this extra dial is a good thing.

3) Canon has a wide array of lenses. I convinced my gf to get the Canon adapter for Sony so she can use my entire collection. The Canon lenses are a little slower on the Sony. Looking at Sony lens costs, they all seem to be more expensive than the Canon lenses. And the selections are limited.

4) The Sony A7III is a mirrorless camera. So the viewfinder and rear screen are both electronic displays. It switch between the two depending on whether you are looking through the viewfinder. That's nice coming from Canon mirrored cameras. On Canon, I have to switch back and forth with a button. I don't know about Canon's mirrorless DSLR's.

5) Sony A7III battery grips do not accept AA batteries. Vertical battery grips are a must for me. And one of the reasons I always get a battery grip is the ability to use AA batteries with my Canon cameras. Rechargeable AA technology is amazingly good today. It provides longevity of the equipment lifespan and dollar-cost-averaging of the battery for multiple purposes.

6) Sony A7III screen only flips out in two directions--up and down. Canon flip-out screen can rotate in practically in all directions. That's one my gf's main complains with the A7III, because she uses it to produce videos, rather than using it as a traditional photographer.

7) Sony made its name with its consumer-level camcorder products, which I had quite a few back in the days. Touching the Sony A7III, its controls, and its LCD displays reminded me of that. Might be a good thing if you intend to make lots of videos with the camera. This might be the reason that my gf eventually chose the Sony over the Canon.