Neither. The most reliable indicator of the kind of person you're attracted to, no matter what gender you are and no matter what gender you prefer romantically, is your seventh house. The sign of the seventh house, planets in it if there are any, and the placement of your seventh house ruler, all give a rough sketch of the kind of personality you're attracted to. What do they bring you? What do you need from a partner? Look to the seventh house for that.
It's common to have a pattern of being attracted to people whose charts reflect your seventh house. Maybe your DC sign is their rising sign, or their sun sign, or their moon sign. Maybe your DC ruler has a prominent place in their chart. Something like that.
But the key thing is that they show you traits that match your seventh house.
Venus indicates how you love and relate. It very generally describes how we attract others and what we find attractive in others, whether those others are romantic interests or simply friends. It's also the feminine planet. The anima, in Jungian terms. If a heterosexual man suppresses the feminine side of himself--his Venus--he tends to look for it in women, and be attracted to women who manifest it.
Neptune is the planet of impossible ideals. Sometimes people project impossible ideals onto their love interests. That's a Neptunian thing. So is the experience of falling in love, when the person you're in love with is the most wonderful thing ever to you. That doesn't have to be unhealthy, but it can be if you keep yourself stuck on the rose colored glasses.
So both Neptune and Venus can be involved in attraction, but unless they're part of your seventh house picture, neither is the main descriptor of who you're attracted to.