Sorry about the wall of text.
Okay, now that I've used my new headphones for a bit, here's how I think I'd compare them. One quick caveat, the only aspect I have absolutely no idea is the mic quality. I've never tested the mic on any of the headphones I own.
Compared to the H9, I found the touch controls to work better on the ST. I'm not sure if I might have gotten an H9 where the touch controls didn't work well, but they were never great for me. The only thing that it consistently registered is turning transparency on or off. Ironically, that is the only aspect of the touch control that I can't hit every time on the ST. Instead of turning on transparency, it usually pauses the track. I may just need to play around with it, yet, I don't really use transparency anyway. Additionally, something I was mildly concerned about at first was that the sound quality on the ST I had read wasn't as good with the ANC on. That may still be the case, however, the headphone itself is so sound isolating by itself, that I haven't found a need to even turn on ANC. I'm wagering that by the time I need ANC due to a loud, constant background noise, I probably wouldn't be able to tell what small difference there may be between high quality mode and ANC on. As part of how isolating the headphone is by design is that the earpads do get hotter for me compared to the H9. The cup itself is also smaller, so I can see why some reviews mentioned they didn't get a great fit due to their ear size. Regardless, I'd rate the overall comfort higher than the H9, especially due to the headband being significantly more comfortable for me. The build quality for both were great. No real complaints for either, though I would give it to the ST due to the headband being better designed. Lastly, the bluetooth works much better on the ST. When I use the H9, I couldn't easily leave my phone say on the 2nd floor and then run down to the 1st floor. I'd usually lose the signal going between floors and sometimes between rooms. So far, I haven't had that issue with the ST.
Now compared to the Clear, which I'm guessing is somewhat close to the Bathys, here's what I think. Build quality is better on the ST and H9. I didn't like how over time, the earpads and the headband on the Focal can get dirty and pretty banged up. Another potential problem with the Focal is that there's a risk of the headband snapping in two. Even though the ST use a synthetic leather, I'd be surprised if they don't hold up better than the Focal. I also doubt the headband will snap in two (I think that problem is mainly a Focal thing). Comfort wise, I found both my Focal and the ST to be similarly comfortable. I'd even give it to the Clear because of its open design with my ears not heating up at all. Obviously there's no real sound isolation on the Clear, let alone ANC, but that shouldn't be an issue on the Bathys you own.
For a sound comparison, I'd leave that to people with alot more experience hahaha. I'll say that to my ears, the ST beat the H9 in all aspects. I know this experience probably won't help as much, but going from the H9 to the ST was a similar degree of difference going from the H9 to the Focal Clear which is to say what I feel is a large margin. I'd say since you enjoy the Bathys sound more than the H9 already, I wouldn't be shocked if you found a similar degree of improvement or greater going from the H9 to the ST. Compared to the Focal Clear and ST, I personally prefer the ST. Everything sounds more responsive and impactful. It's not by a huge margin, but it's there. They also just sound a bit different overall, though it's hard for me to fully explain. Honestly, the only downside is that maybe the soundstage is a bit small on the ST. That may just be placebo since they are closed headphones. Regardless, I think I'll keep the Clear for now because it would be a hassle to sell them and I wouldn't get much money for them most likely.
Overall, I think the biggest potential issue with the ST is the price. It's quite a bit of money and while better, it may not be enough compared to what you already own. I'd imagine a combo of a more comfortable, slightly better built H9 with sound that's a bit better than the Bathys when in wireless (and possibly significantly better than the Bathys in wired though I haven't tried the ST wired yet). If that's worth the price, try them out in a store or buy from a place with a good return policy. Soooo basically all of that boils down to what I posted earlier hahaha.
Hopefully this helps you a bit.
) for you with your system. Off course the dongles themselves could theoretically affect SQ, but on the Roon thread linked above you can read experiences of people who care about SQ a lot 
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