Most of the point why I instinctively rank people like that is probably related to one goal: how good of a synergy the two of us would have in some pursuit. I guess people who have the same kinds of goals and issues, and are about equally advanced, can give each other a lot of help. A much more advanced person can help a lesser person, as well, but it gets troublesome fast, and it needs some other "binding agent" for the relationship to work. Being at the same level is easiest, as mutual support and companionship forms naturally.
I guess I wouldn't have to think of "better and worse", as most of what I think about it pertains to compatibility.
There's a lot of different views on equality as well. I think you folks have good, balanced views about it as a whole. Equality would then mean that equal people are on equal par with something, but on different level with another thing, and they might have different capabilities and means for ends. I think it's been hard for me to find out how to handle the factual differences between people, given the strong ideas people generally have for fair and equal treatment.
I'm trying to treat people in an appropriate way for every occasion, but it's hard when wishes of the people conflict with the needs of the project. Project might be best served by noticing someone as less capable - perhaps less capable for mostly everything - and giving them a role where they don't do much harm. It would also mean limiting their participation and their interaction. They would feel left out. On the other hand, it would be hard to invent appropriate role for them, if they're unfit. If it's a project that is supposed to combine carefree people interaction and tangible results, it's a hard conflict.
I think marriage is one of such pursuits. People wish it to have "results" - i.e. perhaps good life for children, security, support. Mutual financial help. The two wish it to bring joy and a feeling of participation. Love. Okay, I don't view marriage as a "project" but more of a life-long journey. I'm intending to select my mate so well it'll end in the death of either one of us after many happy and productive decades.
Having a hobby group with a few friends would be another, less significant project.
There's other things too, where desires for results and desire to make everyone feel involved get conflicted, mainly by someone being too incapable in too many ways.
I have to think about this.