yeah... the gesshin 1200 grit splash and go stone is a very soft resinoid based stone. It is very muddy, smooth feeling, fast cutting, and works best with a quick soak. It does soak in a bit of water, and even though its splash and go, its not quite the same as shapton for example. The finish it leaves is misty white and very even.
The gesshin 1500 grit splash and go stone is a true splash and go stone. It, like the 1200, is an alumina oxide based stone. Its extremely fast cutting, harder than the 1200, much slower dishing, leaves a higher polish than one might expect at that grit range, and doesnt soak in water at all. I thought having a true splash and go lineup might be nice, as even short soaking stones can be hard for kitchens, and resinoid based stones can crack over time with rushed repeated soaking and drying (slow drying is essential... they should be wrapped with a damp towel during the drying process). These new stones dont soak in water, and just need a small splash of water to work. This also means they dry quickly.
I also find it easier to get a clean edge off of this stone when compared to our 1200 and 2000.
Honestly, i think our 320 and 3000 are game changers... the 1500 not quite as revolutionary, but is still one of the better medium grit stones i've ever used... up there with our gesshin 2000.
Lastly, its important to note that these stones require a bit of a break in to work at their best. This includes initial rounding of the edges, flattening, re-rounding of the edges, and a bit of sharpening.