] In my particular copy of S&S the introduction asserts that the readers always prefer Marianne's "unaffected emotiveness" to Elinor's more reserved nature. For myself, I am liking Elinor a great deal more, and admire her desire to temper her feelings and actions.

I think that is probably due to the fact that more people are extroverts than introverts. As an introvert, I much prefer Elinor to Marianne. For we introverts, dealing with people is an exhausting business and we like to husband our energy, just like Elinor. Extroverts such as Marianne are like the proverbial candles that "cannot last the night" -- many extroverts literally burn out in early middle age.