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Both, with a slight preference for long hair. Someone with long hair looks more womanly and can often look more vulnerable and attractive. Short hair can be more sexy, it seems to imply (to me) assertiveness and maybe more sexual availability. For some reason (not sure why!) a naked women with short hair can be intensely beautiful and sexually attractive, while a naked woman with long hair engenders more feelings of protectiveness and tenderness.
Long hair seems to say to me she's all woman, short hair seems to say more that she's assertive and still very attractive and maybe a little less submissive.