After 30 years with my original 600 ohm AKG K240 (still the same pair), I wanted some closed headphones as a complement, not as a replacement.
I bought an AKG K271 and wasn't happy at all. Main problem being the noise generated by the sidepieces of my glasses squeaking on the faux leather of the capsules and the constant feeling of listening to an empty sea shell. So, I ordered an AT M50 and haven't looked back since.
Even the trusted K240 hasn't seen much use, lately. But I'm not quite sure if this might be because the M50 is one of those products which exaggerate in a way that anything more neutral can only sound naff by comparison.
Ralf