The plastic they're using (hard-coated polycarbonate) is, I believe, the same plastic used on many of the Nokia Lumia phones which a lot of people say feel much higher quality than other, regular plastic phones. That said, the 5C is the cheaper option and it isn't going to feel as good as the aluminium of the 5S. I don't however think it will be anywhere near as cheap-feeling as other phones (e.g. the Samsung Galaxy S4 which has been described as feeling "greasy").