You make an important distinction.
It seems that some people crave structure and order in their lives, while others find those concepts restrictive. I am one of the former, and it has allowed me to deal with the equity/equality issue in a pretty forthright manner. I tell people up front that I have a boyfriend, who lives with me during the winter and resides out of state the remainder of the year. This guy truly is the "love of my life" and when we are apart we make a point of talking each day.
But my best friend lives locally. We also connect on a daily basis, by phone or text. Depending on his work schedule, we get together weekly or at least on alternate weeks for lengthy play sessions. But our relationship--like that which I have with my boyfriend--goes well beyond sex and other fun times. If something breaks down in the apartment, the best friend will fix it ... or if I am running low on paper towels, he will drop by with a case of them. And if he has an issue at work, he will run it by me.
They both know each other, have been intimate with one another, and periodically all three of us will go to the theater, or hiking or enjoy some similar activity together. I reserve "big L" language for the boyfriend, and "little l" language for the best friend, but in truth I care deeply about both of them. If I need an extra hand (or shoulder) I know that I could call on either of them and they would do their best to be there--and I have played the same role for both of them.
And then there is the third one ... the regular fuck buddy who spends the night once or twice a week. Again, he has a good connection with both the boyfriend and the best friend--sexually and otherwise. We are not as deeply involved in each other's lives, but I have meaningful conversations with him and there is definitely a bond.
We are all different--which goes without saying--but for me, the trick has been to spell out and define the nature and limits of the relationship up front. The role that each has works well for him, given other commitments and obligations in his life. Of course, that may change in the future and someone may want something more ... but this arrangement has worked well for all of us for several years. For me, 'equity' means staying true to the commitments made when each of us entered the relationship.