The Diva Cup seems most popular as it is more commonly discussed on the web and had 12 month return policy so you could return it if it just didn’t work for you – making it a very popular choice. (There is no trial period for Diva any more) However the fact that it is most often discussed is probably due to the fact that most discussion forums are US based where it is found easily. It also tends to be the cheapest, as many stores offer promotions and specials on it from time to time. So people naturally tend to choose the cheapest and most talked about cup. The newer cups tend to be least popular, probably because they are less talked about. But choosing which cup to buy based on price and what others talk about may not necessarily give you the best cup for you.