Only a dumb firebender would wait hundreds of years for sozins comet just to get powered up XD
No bending element is better than the other. They all are balanced in harmony, however each one shines at there best in certain situations.
A water bender in the desert against some firebender (with sozin comet) is dead 90% of time unless they are smart enough to already have mastered bloodbending or know of other ways to get water(lol atmosphere maybe, cactus, or pull all the water out of his body and he die lol). However, with sozin comet it wont be easy to hold down a firebender with just bloodbending due to there powered up body, they will resist bloodbending easier.