I agree SQ and signature comes down to personal preferences.
I try to avoid anything with harshness in the highs as this is a real turnoff for my tastes.
A smooth sound signature & warmth in the mids is generally what i prefer.
Hence my current lineup: ZEROs, M2, Rains.
The reason i dont include the PL50 in this list is because although it is smooth as, the BA of the PL50 cannot come near producing the quality & impact of the bass of the dynamic drivers.