"Point: I'd rather hear my gear than their gear."
Well, you're going to wind up hearing a combination of both. And since each recording adds color to some degree, who knows if the color your headphone adds will clash or compliment. You're safer with a relatively 'colorless' phone being more suitable to a wider variety of recordings, IMO. If you want to add the same color to every single recording, then be my guest. There's no 'wrong' or 'right' when it comes to subjective taste. I listen to a lot of acoustic jazz so I prefer tol go with as transparent as I can get. I've played and listened to enough live jazz to know what acoustic instruments sound like in real life. The microphones in the studio add a bit of color, the room, the monitors, etc. but a well recorded jazz piano still sounds darn close to a piano in real life.....and if it didin't I wouldn't want to have a different set of headphones to suit the color of each piano in each different recording!
"Our eyes are similarly calibrated. Our ears vary a great deal more." How do you know that I see green or red the same way you do?
As for the fact that we all hear differently....that's a given. I want to hear acoustic recordings that sound true to life with 'my' ears, not yours, so I pick a headphone or speaker accordingly.
I've heard this argument many times before, and find it incredibly lacking. You're comparing apples to oranges, for start. Our eyes are similarly calibrated. Our ears vary a great deal more.
Second, have you heard modern recordings? We're not just going from Artist -> Headphones -> Ears here. The "music in itself" doesn't exist; it's been produced, molded, and modified on countless bits of equipment often with pitiful monitoring equipment. It's rarely 'as intended' and seldom made for those with high end equipment. And I'm not talking about just pop music here; I'm talking about darn near everything these days. It's naive to the process (a process I now have to participate in occasionally for work) to think that whatever comes on the disc is "pure music" plain and simple.
Point: I'd rather hear my gear than their gear.
EDIT: I'm frequently reminded of a particular story from Sound by Singer in NYC. 50 Cent was in the store, and heard their RS1 a number of years ago. He loved it, and bought a pair for himself and every record producer that he was working with. Now, what are the odds that this has happened in other situations, and other people are mixing and using something as colored as an RS1 for their monitoring? Frankly, in that case, we have absolutely no idea as to the initial intent of the production. Should we buy the headphone we know was involved in specific circumstances each time? I won't lie, it's partially why I own a 271 MK II variant: I know that every Radiohead album for the past several years has been used in their production and I like to know that I'm listening to it as they heard it in the studio. But other cases? I'll color the music how I like it. I'm a hypocrite, I know.