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Moco-chan is a needy, autistic woman and it makes the protective instinct flare up. Saviourfags will love Moco-chan more.
Fuwawa on the other had has a more traditionally feminine nature to her, and when I say that I mean the 'idealized woman' picture. She's cute, overtly ditzy on purpose, and has much better ability to socially manipulate. No, I don't mean that in a negative way either, it's just a different way of approaching things and women are good at doing that.
It's personal preferences which you like more at the end of the day, but because they're in the limelight, they play up those personal traits to a greater degree, which makes Moco-chan front and center for attention.