Have thought of this a lot and think my line of thinking would probably resonate with many people who have these as part of their identity. For instance, when i was married (to a woman), even though i was gay and that was the most obvious elephant in the room, i came to understand that we were also both bottom and sub natures. So, our chemistry sucked all around (and not in a good way).
i always include both descriptors in profiles and explanations though, because for me, they are different and their order of importance is different too. i have found that that is not unique to me or people on my side of the slash, but i have also found it can be important distinction for Top/Dom people to know about and understand as well.
When i first started exploring D/s culture, i ran into a lot of people identifying as both Dom and sub who had that black or white definition of those predilections that lots of us here in this community have come to relegate to immaturity or ignorance. But i think we all have bias and a natural tendency to be ethnocentric, even with D/s stuff, so it's prolly good to always be aware that we may not be as aware as we think we are.
Sorry, that was a long prelude.
i am "bottom/sub," with the "bottom" part in front (which sounds counter intuitive as i read it). What i mean is, my sub nature follows my bottom nature, and i know it's opposite for others. For me, the more a Top knows about how to 'penetrate' me, the more skilled and connected He is to that process, the more sub i become with Him. And really, "connected" should proceed "skilled." For me, presence and awareness (that leads to connected to my way of thinking), is far more important than "skill." "Penetration" has myriad forms and meaning to me, not just talking about physical. To me, and i think really this is a part of most bottom nature, the best and most powerful penetration is holistic, it involves the whole person, not just the physical. If my observation is correct, i think the opposite is also true, i.e., the most powerful (and pleasurable?) penetration for a Top is also holistic?
Re the order and connection of bottom/sub though... (and this reads way too clinical to me, it isn't, so sorry for 'sounding' that way), the most powerful and effective influencing/handling for me happens when a Top connects and penetrates me skillfully and thoroughly. For me, it's sort of like an avalanche when it happens, or one door opens the other. The more my bottom nature is accessed and handled, the more submissive i become. i have found that things i never would have 'submitted" too initially, are things i am opened to (not open to, opened to), when well 'penetrated' first.