I can only provide some general information as I've never owned either, but I did own a pair of Audax HM170ZO which were very nice. I am a fan of the Audax aerogel cone, as it generally provides a nice balance between good detail without sounding shouty. I prefer the Faital-Pro line for woofers, but this mid seems to use the same dense paper cone that is treated for outdoor use. Therefore, as a midrange. it may exhibit that soft focus that tends to obscure some detail (speculation) There is also a lot more copper in the Audax, as opposed to aluminum. Lastly the Audax HM170 is a legacy product (likely produced mid 1980's or earlier) while the Faital 6RS is a more modern design, for what that's worth.
