What I will say about this - my fantasy really struggles in the market. Waters and the Wild has never gained traction (partly due to the key oppotunities in NI not coming to fruition due to publisher issues) and my current one, whilst getting a reasonable response is struggling to find anywhere solid to place it. My sf outsells my fantasy about 20 copies to one, and that's generous.
Inish is the biggest individual seller but with the trilogy, there is a catch rate of read ons that buy all three. (In fact, pretty much any sales of book 2 are matched by a sale of book 3 about 3 days later, so I know that Sunset takes around 3 days to read and has close to a 100% pull in for Legacy).
Which means, frankly, I have to wonder why bother writing fantasy. I can't see me doing anymore in the near future (which is partly down to what I have a market for/what I'm working on/what I might get funding for) and, after being told by an agent recently that my offering was too diverse, I can't see what benefit it is for me to do so.
I suppose, if I loved writing fantasy more than sf, I'd want to do so anyway. But I prefer writing sci-fi - and it is a pretty cool thing to have on a resume when people ask what I do - so I probably will. And I'll probably revisit Abendau (thinking of an Ealyn-Empress-Darwin prequel at the mo). And, if it would sodding work, the Inish world.
TLDR: it might be true that, as writers, we find a niche in the market that likes us and it pays us to learn to work in that niche rather than all over the place....