My experience...
6-oxo is a much "milder", but effective AI compared to ATD.
With 6-oxo, your est levels won't crash to near zero and which is why libido is not effected.
ATD is a bit stronger AI, and your libido may take a hit if dosed to high.
This would be the AI of choice if used on cycle with an aromatizing compound.
In PCT, it has the worst rep for killing libido, but the best rep in keeping est levels down.
PCT...I always use 6-oxo, or 6-Bromo AI's.