1. X发烧友 发烧友 [fā shāo yǒu] 对某项事业或活动非常迷恋专注的人；狂热的爱好者。 fancier; zealot; enthusiastic fan 2. X迷 迷 [mí] 沉醉于某一事物的人。 fan; enthusiast; fiend; maniac: a chess enthusiast; 棋迷 a movie fan; a film fiend; 影迷 I personally thnik that 发烧友 is a stronger word. A 体育迷 enjoys sports while a 体育发烧友 would like to do much more things for his sports, like buying a complete set of top-tier equipment.

vice versa, it's 体育发烧友 is used for formal writing

hi there,羽毛球发烧友^_^

体育迷, 音乐迷， ‘迷’ - a neutral word 体育发烧友， 音乐发烧友， ‘发烧友’ - similar with 'fanatic' , initially from the English word 'fever'