In recent years, much has been made of the improved sleeping comfort that started with Westin’s “Heavenly Bed.” The next frontier, it seems, is pillows. The Benjamin, a Manhattan hotel, now offers a choice of 12 pillow types, overseen by a “sleep concierge.” They even come with a guarantee: money back if a guest doesn’t sleep as well in the hotel as at home.The Franklin’s pillow menu includes the “Snore-No-More,” which holds the chin up to open nasal passages. A reported 75 percent of guests try one of the special pillows.