Ghalabat al-raʾy is not a guess or arbitrary personal taste. A reasoned preference considers usage, the relevant revealed texts, other authoritative evidence, and the strength of the reasoning. A stronger interpretation is called rājiḥ; the alternative may be described as marjūḥ.
Merely saying “I prefer menstruation because it feels right” would not establish a juristic interpretation. The learner should understand the methodological point: preference must be grounded in reasons, not taste.