I have B+W/Schneider 10-stop NDs, they're good but not true neutral, they have a warm tone.
mine is a cheaper Haida 10 Stop Pro II MC (Schott glass).
he has a light blue tone. at least the non pro version has, as reported.
i have not noticed that yet with my few testshots out in the garden.
after some reading i decided to safe myself 70 bucks and go for the haida.
no matter if warm or blue tone you have to adjust in post anyway.
and those who have both filters wrote they don´t see any other difference between a B+W and the haida.
small test (not mine):
i will have to do more testshots today but im pretty satisfied so far.