I've tried many inner carbon blades past few months, to name a few here:
- Sanwei 75 inner
- Sanwei 75 inner PBO
- Sanwei Vita ALC
- Xiom 36.5 ALXi
- Nittaku So-ten
So far, my favorite is the So-ten. Composition-wise, it's really close to the W968, please refer to the attached picture here. The top limba plies are a bit thicker, while the 2nd ayous layer is thinner, so it's a tad softer and slower. At first, the blade seemed underwhelming, but it grows on me. Doesn't have the W968's killer FH, but much more balance and with appropriate technique, you can still get loads of spin and speed on both FH and BH. The handle is thicker than W968, but thinner than Viscaria. And for shot qualities, it stands in between those 2 blades as well:
FH: W968 > So-ten > Viscaria
BH: Viscaria > So-ten > W968
I can see why it's not a popular choice for top players, but for amateurs, the So-ten should be a solid choice, given its balance and good control.