Some contradictions here:
…and no amount of advertising will ensure customer retention
While emotional design alone does not make a product great…
Though, if I have to choose, the former is much, much more important. Great marketing on a mediocre product can yield great profits (ie. some Apple products)
While its true the site has to look nice and professional, I feel that is just cherry on top of cake. The cake has to taste damn good for it to sell.