It is a great question. Unfortunately I don’t have a clue of the answer, if controlling for the obvious (hair retained by fin).
As Melvin said, we can assume having hair tends to be more attractive than a balding look, but as for other, more subtle or ineffable effects of finasteride on attractiveness - who knows? I can’t say I’ve seen any evidence for it, or against it. I think the default assumption is that there is no effect unless proven otherwise, but I can’t rule out the possibility.
Human attractiveness seems to be affected by little changes in pheromones, hormonal cycles etc. Women’s monthly cycle debatably have some effect. So I don’t know.
Personally I wouldn’t worry about it. If it helps your hair and your confidence that’s probably the most important thing. And if it prevents your prostate getting too big.