so basically think about it you have

Water: Has healing capabilities extreme cooling and the ability to turn salt water into fresh water pretty practical element if you ask me also is good offensively as well if near water an experienced bender could bring a wall of water down on someone and flash freeze it also they have the ability to super heat water to steam in seconds seeing how fresh steam can sear flesh it could boil you to the point of going into shock and even death bring blood bending in and you have a pretty versatile element survival skills defense and offensive moves.

Earth: Ok so earth can build structures quickly has solid defense and a good offense as well but with one major difference water benders can demobilize enemies but earth can obliterate an unaware or weaker foe a boulder can kill on contact if big enough and they can carve rock into spikes so bonus points earthbenders would be necessary in a war as they can use there powers as overcharged ballistas with no weight limits if used in unison. A master earthbender could obviously decimate any structure or piece of land it would have an obvious advantage against an airbender of equal caliber being pacifists they would not be able to stop the onslaught of attacks.

Fire: And now we come to fire this element is mostly associated with destruction and that is where it is it's strongest it has the strongest martial arts form it is offensively a great element bt trying to survive using it would be incredibly difficult if stranded somewhere in a fight firebending if mastered is the best but as an element it is one of the weaker but its cool as hell aesthetically

Air:an element of absolute peace those who master this element are pacifistic by nature at this point wanting to avoid a physical confrontation by any means but if it would come to pass air has the ability of air boosted jumps glider assisted flight strong projections of air currents and the ability to compress air to stop projectiles