Water for me, not just because I enjoy water over fire in general, but because in competative play, they're so amazing. Bulky Waters can pull off fantastic stalls as tanks and team support. Things like Swampert, Suicune, Milotic, and Vaporeon are some of the best things to take hits; Suicune especially. Water also makes an excellent typing having only 2 weaknesses and resistances to things like Ice, Water, Fire, Steel, etc...Fire, however, cannot play defensive roles on teams. And offensively, they are walled by a lot of common tanks (bulky waters come to mind lol) Weakness to rock, ground, water and Stealth Rock weakness hurts them a lot as well.