Good Day adrspach.
I just registered here, so I can give you a little answer.
(so far I´ve only read, not written)
I am from germany and have several Shaptons, Naniwa and a Cerax, as well as a Suehiro.
First off an overall descripion of the stones:
Naniwa Superstones tend to be kind of soft. I heard bad reviews about a 220 Superstone, saying it is way too soft for such a coarse stone.
Others don´t semm to bother and the Naniwa SS 1000 is commonly used amongst german razor fans.
Personally I prefer harder stones for coarse sharpening.
I do own Naniwa SS only in the range of 8.000 and 10.000, I sold my 3.000.
Naniwa however has another line called the Chocera. They seem to be alot harder in the lower grit range, making it somewhat more attractive to me.
Shapton stones can be devided into two series:
The Hano Kuromaku (called professional series) or the new glasstones.
The professionals are brightly colored resin bond stones, as well as the naniwa. But the resin used is way harder. These stones tend to be very slick, without that much feedback.
I however think the Shapton Pro 2k and 5k are an exception of that,
because they do give feedback.
The Glasstones are made of ceramik material glued to a glass plate.
These tend to be slick as glass and extremely hard as well.
The Pro series seems to make a little more hazy finish,
not quite japanese natural Stone finish (called kasumi)
but not mirror as well.
The Shapton GS 500 kombined with the GS 2.000 has been recommended as quick, efficant and enjoyable way to start.
Cerax, wich also produces Suehiro stones, I think are quite uncommon in the US, right?
They are a bit underestimated, I think.
I own a Cerax 1k/6k kombi that I really like. It is the only combination stone that I actually use.
The 1k is my only 1k and does his job very well.
The 6k side is quite hard, but not as hard as shapton
and does deliver considerably more feedback than shaptons usually do.
I also owned a suehiro 8.000 gold some time ago.
It was a very big, extremely nice magnesia bond stone.
It gave an excellent 8k edge and merely had to be lapped.
I however substituted it with a Naniwa SS 8k,
becaus unlike at lower grit, in higher grits (not ultrafine grits)
I prefer softer stones
For very coarse works below the 1k I usually use wet sandpaper.
It works way faster than stones at a fraction of the cost.
good question, id also be interested to know more about the Chocera if it's part of the discussion.