A Wikipedia tem bons artigos sobre as duas tecnologias 802.11 e Bluetooth technologies.
Resumo rápido da Wikipédia sobre as diferenças :
Bluetooth and Wi-Fi have many applications in today's offices, homes, and on the move: setting up networks, printing, or transferring presentations and files from PDAs to computers. Both are versions of unlicensed wireless technology. Wi-Fi is intended for resident equipment and its applications. The category of applications is outlined as WLAN, the wireless local area networks. Wi-Fi is intended as a replacement for cabling for general local area network access in work areas. Bluetooth is intended for non resident equipment and its applications. The category of applications is outlined as the wireless personal area network (WPAN). Bluetooth is a replacement for cabling in a variety of personally carried applications in any ambience.
Então, basicamente, o 802.11 é um acréscimo à rede e conexão de computadores & smartphones que suportam alta largura de banda e abrangem grandes áreas.
O Bluetooth é uma tecnologia sem fio ad-hoc que funciona a baixas distâncias, tornando-o perfeito para transferências de arquivos e hardware de controle remoto.