I was the one who preferred the M40f/s over M50
I traded the more expensive M50 for a set of M40f/s on this very site.
Don't regret it.

My monitors give pretty good representation of bass for final decisions, and the 'extended bass' of of the M50 throws my mixes off. Could just be me.
But for a reference (one that translates) the M40f/s work better for me.
This is HIGHLY a personal preference.

Again, using trusted monitors for final decision is important, but having a set of headphones you 'know' and can easily adapt to is helpful also.
You don't know what works best for you until you try them.

I do not work here, but the benefits are still awesome
Make your sound your own!