ND filters. Most neutral. What's the veredict ?

I'm finally buying "my" 24TSE. I've read a lot about ND filters without getting to be sure about the most neutral in color of all 7 to 10 stop ND filters. I would sacrifice some neutrality for the one which inflicts the least blurring.

I know that these filters are hard to get in 82mm. I want to go this way as I encountered before numerous light leaks while using a drop-in filter.

All comments and information will be greatly appreciated.

Eduardo