I have never been able to disconnect the two. The one will always interfere with the other. But that's maybe a girly thing.
The mind. Without an intellectual connection the chemistry is dead in the water for me.
As to suitability, there's always risk isn't there? I have never quite worked out how to do a risk assessment on any relationship and actually, now, I don't feel the need. I cannot consider what will happen ad infinitum, only whether there is a positive connection and potential for mutual pleasure and growth as a person. Hurt, it seems to me, is almost inevitable even when bitter sweet.