Thanks for all the help, everyone.   A few takeaways:   The most important task (or at least the one that allows me to justify spending this much money) I'll be using these headphones for is production of my own work. It seems that neither pair mentioned is terribly appropriate for that...

Thanks for the input.   Although one of the downsides of my current living situation is a more-or-less untreatable listening environment in the form of my bedroom, one of the upsides is that the house is full of musicians, and there are some relatively well treated rooms with above average...

Thanks for taking the time to read this, I've finally registered and posted here tonight after lurking for some time, as I'm closing in on a decision and now have questions specific enough that searches of previous discussions leave me wanting.   I'll soon be purchasing a pair of headphones...