That said, SolidJS as a whole requires a completely different mental model of rendering, even if it does look superficially similar to React. It's also a much smaller ecosystem, with less documentation, so getting to grips with it is that much harder. Very rewarding, but probably not ideal for everyone right now.
Oh, I didn't know that about Vue. Eww!
Having lots of tiny components makes it harder to see the big picture.
Too big and too small are both bad, there's a balance you need to find. Components should be small enough to fit in your head, big enough to represent ideas. The difference is that it's natural for big components to be broken down into smaller ones when their size starts to cause pain. But nobody goes around merging smaller components into bigger ones to make them more readable. When your components are too tiny people just suffer through the pain and develop Stockholm syndrome.
> I'd try and fit more and more stuff into a single component until it the pain of maintaining it was greater than the pain of splitting it
I understand that it seems painful, but this is actually a great workflow: it forces the decision to split to be based on the real pain, not on your fantasies about future pain. Pain is a tool that helps you make good decisions. In that sense React is like Perl: easier to write, harder to reason about.
This isn't a theoretical concern either. Like I said, I've had this issue with Vue before, and component sizes just bloated to the point where many pages were just single, chaotically interwoven components with dozens of state variables that theoretically were never used by each other, but in practice tended to be shared accidentally or out of short term convenience. At which point all bets are off and every bug becomes an exercise in figuring out what's going on.
That's not to say that that's a Vue-specific problem, because I've also had that issue in other frameworks, including React. But far less often in React, because it's much easier to deal with the pain when it starts with a simple refactor, than dealing with it a year and several new features down the line when everything is tangled together like a headphone cord in your pocket.
I'm surprised you see that as a disadvantage, for me that's always the biggest advantage of JSX-style syntax! I don't want huge components that do everything, I want components to do as little as necessary to be actually useful. It's the same as if I were writing functions: keep them fairly small, make sure they're doing a specific thing usefully, and then compose them together like Lego bricks.
When I was doing more Vue work, this is one of the things that I struggled the most with, that splitting one component into two components required a load of boilerplate and a whole new file. (And that itself was a big improvement on Angular, which usually had multiple files doing different things, at least when I was last using it). This inevitably meant that I'd try and fit more and more stuff into a single component until it the pain of maintaining it was greater than the pain of splitting it. (At which point it would usually be a lot harder to extract the would-be child component than it needed to be, because I'd left it too long.)
I think the rest is mostly just syntax preferences. Like you say, you can write bad code in both cases, and I think a lot of it comes down to which matches better to your mental model if what HTML generation looks like. But being able to easily start a new component, just like starting a new function, is such an important benefit of JSX, for me at least.