Hi! Thanks for reading and for the question!
I've already written an extensive review of the Custom One Pro right over here. I'll link it just in case you haven't seen that yet:
Out of the models you're looking at, for all-day comfort I'd definitely lean strongly in favor of the Custom One. It's dramatically more comfortable than either of the Audio Technica models.
Both the MSR7 and the M50X do have sound that's considered closer to "accurate/flat," but the Custom One Pro isn't so far off the mark that you'll be upset...especially if it's for background music listening and not professional audio work.
If you manage to buy the headphones from a place with a good return policy, like Amazon or a few other online shops, you can test them out in the comfort of your house, and worst-case pay a small restocking fee to return them if you don't like them.
Hope that helps you out!