I am utterly confused about this too.
My feelings towards T can be completely disproportionate (I can be intensely angry over almost nothing or feel completely in love with him after a good session) and this sort of suggests transference, yet I do feel I know him quite well, he is quite open so I feel some of this must be genuine affection for him.
I try to imagine how I would feel about him if I had met him in a different context, but it's impossible to say.
I have also spent months thinking that I couldn't work through my feelings for him in therapy because he is uncomfortable with my feelings. It is only now that I am seeing another T about this attachment that I realise it is actually me who is uncomfortable talking about the feelings. I even tried to project that discomfort on to new T!
I truly think that these feelings towards our therapists can be both; I love him as a person, for who he is, but I know these feelings have only emerged because he has fulfilled needs for me that have been unmet throughout my life. So it is transference, but that doesn't mean it isn't genuine love.