Why does the word dilemma have two pronunciations?

According to Oxford Dictionary (http://www.oxforddictionaries.com/definition/english/dilemma) Pronunciation is : /dɪˈlɛmə, dʌɪ-/ Which is di-lema or dye-lema. The website "howjsay" (http://www.howjsay.com/index.php?word=dilemma) also gives two pronunciations. Which one is correct for...