I also find the 009 more tonally correct (in the sense of sounding tonally neutral) than the 007mk1, but that's driven from the stock 727 amp.
Having said that, there is no question the
Mk1 strikes the best balance between correctness and masking of unpleasant nature of some (many depending on you fav music genre) of today's recordings / true tone of some instruments (ever heard a trumpet or violin in real? It's not necessarily silk and smooth at actual loudness level
The 009 does not suffer of sins of commission like many a headphone do (because unfortunately, it's all a matter of compromise like ever other man made imperfect designs...). But the 009 also does not suffer sins of omission to please the ear at the expense of fidelity.
As such, the 007mk1 is much more accomodating of bright / harsh recordings or listening sessions at realistic and/or ear splitting volume levels.
In my not so humble opinion (why should an opinion be humble?), the 009 excels at low to moderate volume levels for moderate to excellent quality recordings and is the most chameleon like headphone I've heard (in the sense it's pretty difficult to hear the same sound characteristics coming back recording after recording).
The 007 is much more tolerant of music genres and listening habits while, apparently, giving very little away to the 009 when properly fed.