If it's real, then who has better gaydar, lesbian women or straight, can be just as validly determined.
The expectation is that lesbians will have superior gaydar due to their experience of choosing partners would be more tuned in to others orientation - but that could be a negative filter. Gay people tend to overestimate the prevalence of gay people. A group of scholars conducted a study which set out to reveal who has a greater interpersonal sensitivity.
In-group advantage for accurately judging sexual orientation by judge and target sexual orientation. Credit and link: 10.1080/02699931.2014.890093
The study entailed a mixture of lesbian and straight women watching video clips of a target group of women discussing family relationships and future life. The watchers were asked to rate multiple aspects of the target group; what were they thinking? What emotions they experienced? What type of personality did they have and overall were they gay or straight on a continuous scale of homosexuality? Who was most likely to get Ellen DeGeneres, Portia de Rossi and Ellen Page all correct?
Contrary to expectation, straight judges made more accurate assessments of thoughts and emotions, leading to speculation that lesbians might be easier to read due to non-verbal communication? Lesbians won out in terms of gaydar, they spotted their own orientation more easily and the authors suggest the the prominence of sexuality for lesbians enables a fine-tuned awareness of others sexuality while straight women were instead more interested in thoughts and emotions because the sexuality of other women seems to bear less importance for them.
Citation: Mollie A. Ruben, Krista M. Hill&Judith A. Hall, How women's sexual orientation guides accuracy of interpersonal judgements of other women, Cognition & Emotion, DOI: 10.1080/02699931.2014.890093