I'd say that HTTPS (or TLS in general) is more problematic, since you need to trust numerous root CAs in machine/browser store. Sure, you can use certificate pinning, but that has the same issues as SSH host key verification.
Compare that to malware that just copies a developer's ssh private key off the disk (again, almost nobody ever password protects theirs). This just happened recently on a massive scale with the npm attacks. Or intercepts the first connection from a client host and, again, because nobody ever validates keys, injects a false host key, and now they're pwnd indefinitely. Or, again, companies that do not strictly validate host keys, meaning immediate MitM. There's like a dozen ways to compromise SSH. It doesn't have to be that way, but it is that way, because of how people use it.