sure it's a little bit about what your personally like.
but for me? I don't consider a character with the breast and a penis to be a futanari, I consider them shemale slash dickgirls if they don't have a vagina.
otherwise? what's the difference between that and a famboy, that they have breast?
do you see what I mean?
additionally the reason I like futanari is because they are able to reproduce both ways, so they're able to impregnate and get pregnant themselves.