Formatt ND filter experience?

No reaction in a brand-specific forum, so I'll pose the question to a broader crowd:

I'm looking to get a 77 mm threaded very dense ND, in the range of at least 1.8 (6 stops) to 3.0 (10 stops). B&H lists both B+W and Formatt filters in this range. ( http://www.bhphotovideo.com/c/search?ci=114&N=4289364308+4294951125+4294951124+4294955264 ) I'm familiar with the B+W brand, and somewhat familiar with Formatt rectangular filters. Does anyone have any experience with the Formatt screw-in filters in terns of the characteristics and quality of the mounting ring, compared with B+W? Anyone know if the outer ring is threaded?

I'm assuming the glass in either would be beyond question (both Schott), but neither is multi-coated. I would think multi-coating would be of particular value with a very strong ND, since flare would potentially be a larger proportion of the light reaching the sensor. Again, any comments on the optical quality and need for coating would be appreciated.

Dave
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