I want to have a really refined edge that's good for cutting, but happy if it doubles as a polisher when thinning. Currently my highest stone is a Shapton Pro 5k and while I get good results with it, it's not amazing to use and maybe not as fine as I'd like.Do you want to highly polish your edges or have a refine edge with teeth ?
First I would go Naniwa super 5k or 8k (5k is fine enough)
Second I would go to a naturals, BBW or Coticule is good advise, those stones are great and a big BBW is about 80 euros. But I feel a BBW is maybe 4k at best and coticule is 6k at best. A good Jnat big enough koppa (to reach the 8k) can be find for about 150/200 euros. With synthetic, maybe a imanishi/kitayama 8k.
I got the morihei 8k.. not impressed, it is quite slow and finish is not amazing. Work a bit like bester 8k but it is much more expensive.
Personnaly, I like the Naniwa 5k and I am ok with the feeling (which is close to naniwa super stones), it is gummy a little but that stone is fast and give a great finish. Compared to a Naniwa super, it will be a faster stone, no clogging, less fine at same grit.
Hmm, I’m tempted to go nuts with it just for the sake of it (kind of abandoning practicality) and consider some 12-16k, but I think that’s a quest for later.
Wow, thanks for the thoughtful and informative response.What sorts of knives/steels are you trying to work on, and what are you cutting with them? Wide/single bevels vs. monosteel? 10xx / Shirogami vs. Aogami / 1.2562, etc? Making salsa vs. sashimi, etc?
I ask this, as no stone behaves consistently on all steel alloys/hardness's... Edge bevel sharpening typically has different needs than wide bevel polishing, and wide bevel polishing has different needs than monosteel polishing. Furthermore, some steels plateau at higher grits than others in practical use, and some ingredients respond to certain edges better than others.
In terms of the debate between synthetic vs. natural finishing stones... Honestly, I've spent a lot of time and money chasing both. As I said, no single stone behaves the same way on all knives, for all jobs, whether it was made in the ground or made in a factory. Sometimes, you can get a single natural stone that's actually more practical and effective for a job than a synth (Or collection of synths), and other times not... The main difference is, there's more sample variation with natural stones. One person might have a bit of a dud Coti that's a bit of a doorstop. Another might have one that peaks out closer to 15K. I know, because I have both, and various in between. However, my 6K Cerax, is probably the same as the one you'd buy anywhere in the world, from any seller.
Your needs are specific. A popularity contest isn't the way to find what you need.
From your list, I've got the Cerax 6K, and used to own a Shapton Pro 5K & 8K. I also have a Naniwa Chosera/Pro 10K, which could probably pick up from your Shapton Pro 5K without a lot of problem.
The Suehiro Cerax 6K (Orange) is a pretty well balanced stone. It's a soaker, but not a fussy one. It's a good compromise in many situations, but at the same time, is seldom the stone I'd pick if I was searching for a specific area of performance... 6K synths at their best, are trying to be balanced at everything for kitchen applications, but are starting to make some compromises. It can create a halfway decent polish with a bit of pressure on hardened steel, and a pretty okay haze on some claddings. It's in sort of a goldilox zone for hardness... Not horrible for dishing, or flattening, and only starts to convex edges on fairly soft steels. At its best, it's not a horrible edge, or finish, but it's almost never the final destination I was searching for. A sort of jack-of-all-trades, master of none... However, if that's what you're looking for, it's not a bad stone at all. I maybe made it sound worse than it actually is.
For me, the Shapton Pro 5K is a good transition stone on woodworking tools or straight razors, and the Shapton Pro 8K is a good pre-finisher for either of the aforementioned... Neither are happy places for me with kitchen knives. Very consistent, but bland edges for their grit. Horrible for polishing wide/single bevels. Too hard, no contrast... If you're not happy with your SP 5K in the kitchen, I actually probably recommend to step down to the Shapton 4K GS HR for edges. It's a nicer balance of tooth and polish. Hard, so you get a nice, crisp bevel, still. Not as slippery as the SP 5K, so you can maintain that bevel a bit better freehand.
The Naniwa Chosera/Pro 10K (Closest I can reference to the Naniwa Snow White 8K.) is an interesting stone... Very fast cutting for its grit. Can pick up from a 5-6K stone no problem. Bad finish on wide/single bevels... At the same time, this is a synth that's finally starting to get into the finisher range for razors and chisels for me (I.E. push-cutting tools.)... A decent edge for parers used for peeling, and micro-bevel for single-bevels, just barely. Not a great choice on higher-carbide steels (HAP-40, or even Aogami Super.), and sort of overkill for softer/simpler alloys (Like <60hrc 10xx.). However, it's just barely starting to transition you into a different realm of sharpness, where you can cut a tomato not because the edge is 'toothy', but because the apex is starting to get incredibly fine. Afterwards, you start eyeing up Shapton 30K's and sub-micron pastes, trying to find where that sort of edge culminates. It's another rabbit hole...
Hopefully this helps.
It will be a variety of steels, not just of my own collection, as I am sharpening for other people too which is why I was looking for a general opinion. That said, I’m not looking for the perfect stone for all jobs, just looking for somewhere to start while I expand my collection and start branching out from the series of SPs I have, perhaps doubling as finishing stone after thinning. I know my next ones won’t be the last stones I buy.