First of all, you can only listen, evaluate one item at a time. You can not evaluate bass and treble at exactly the same time. Your brain switches back and forth. Yes, the most pronounced differences will attract your attention first. So you just switch your attention to other facets.
I A/B high resolution files to vinyl all the time. I mean 24/96 and 24/192 files. In doing so with my friends it is interesting that there is, without discussing it first, 100% agreement as to which is "better."
A/Bing equipment is more difficult if not down right impossible. If you have a good relationship with a dealer he might allow you to borrow electronics to A/B especially if you are a big ticket buyer. Even so it is very unusual to be able to A/B speakers in your own home and they are the most determinant part of any system.
Listening to one speaker for a week then listening to another speaker for a week is not a good way to evaluate minor differences between speakers because we accommodate to sound. Switching back and forth is always the best way to evaluate equipment but difficult to arrange. There are situations where there is such a profound difference in performance that there is no question which device is better. Then it becomes a no brainer.
