By coincidence I just spent several hours today comparing exactly these two services (Wasabi vs B2) and even though I am familiar with Backblaze and have used it before, I went with Wasabi. It's basically the same price, has more regions, a very simple interface, and rather than having to manage both hot and cold storage Wasabi is cheap enough to just throw everything into hot.

The only downside I found is that they limit free egress to 100% of your storage (so if you store 1tb, you get 1tb egress). In practice I don't think this will be an issue for my use case.

So I'm an example of a person who this morning had almost never heard of Wasabi, knows Backlaze well, and after an hour or two of research I have completely switched over.