Most players start out the game wondering which magic is the best to use relative to all the others. The truth is that each magic has its benefits and downfalls, and picking one is simply a matter of your playing style.
Fire has the fastest Q attack in the game along with Water and Shadow. All of Fire's attacks leave the Burning effect, a slow DoT that increases with the power of the attack and can be put out by the Soaked effect. Fire's R is a medium speed and can only be used in specific circumstances. Flame Splash is a great melee because it jumps you up in the air so you can get a bit more leverage on your attacks and provides great strategic advantages. Burning Soul is good for exp but not much else. Flame Barrier can be put out instantly by any water attacks, but that water attack will still be blocked, even Tidal Dragon. Fire's ultimate shoots out mini fireballs which can rack up a lot of damage if all of them hit. It is best used on a target on the ground as it has a large AoE and leaves behind a powerful burning DoT, often killing anything fortunate enough to survive it, save for the most powerful of NPCs.
Lightning is probably the most commonly used magic in the game. It is a very easy magic to get a grasp of for new players. It has the highest base damage of all the magics but has a medium speed and the highest energy cost. All lightning attacks leave the Shocked DoT, which is very fast and can be enhanced by the Soak effect. All lightning attacks gain slightly more damage if they hit a soaked target. Its Q attack is instant, however sometimes inaccurate. It has the ability to stopping single-projectile/jumping ultimates if you time it right. It's E and F are nothing special, just a run of the mill grab attack. It's R is quite slow and shouldn't be used too often, it also takes a massive amount of energy, putting you at a strategic disadvantage. Its ultimate has the highest damage out of all the jumping ultimates, but is slow and hard to aim, you could easily be killed while simply charging it.
Light is similar to lightning. It is relatively common and can pack a punch considering its Q is also instant. Its Q attack takes the same time to cast as lightning, but takes far less energy because it does not leave a DoT The range of instant cast magics is limited, however. It's E and F attacks are nothing special. Its R attack takes a medium amount of time to cast. Light's ultimate is probably the one with the most damage in the game right now. It has by far the highest single target damage in the game, reaching past even 5000 damage if fully charged on a maxed mp user. It is the perfect counter attack to jumping ultimates (which it can even stop dead in their tracks mid-air) and R attacks. It also destroys ships extremely fast. The only downside is that its projectiles have virtually no AoE, unlike Firestorm which is quite the opposite.
Earth is quite unique. It has by far the highest AoE range in the game, its Q attack is almost like a projectile based R attack. It does medium damage. Its R attack is quite slow and leaves no smoke. Its E grab isn't very good, but its F is extremely good as it leaves the target directly below the attacker allowing them to punish them with a sword. Its barrier can take the most punishment out of any barrier in the game and has no specific weakness. However, Earth's Ultimate is abysmal and by far the worst in the game. It is a jumping ultimate, but it shoots 2 projectiles slowly. Each does a small amount of impact damage and has a medium AoE, but if you use both projectiles on top of each other it only does one's worth of damage. If you're very skilled, you might be able to use this to chase runners, but that's about it.
Wind is even more unique than Earth. Its Q attack has the highest range and projectile speed out of any in the game, but also the lowest AoE. However, this attack knocks people back, as does all of Wind's attacks. It is the ultimate magic for recovering any sort of stat like energy or stamina as you can blow your enemy away. It's E and F are okay. Its R is the slowest in the game and is not really useful in any situation. It's ultimate shoots a giant tornado and has the fastest cast time out of every ultimate. This tornado can hit up to 4(?) times, each roughly damaging for about 1/3rd of your Q attack. It is likely the most rarely used magic in the game. The ultimate can be used to create whirlpools and is capable of launching opponents a massive distance.
Shadow is almost like a dark version of Fire. All shadow attacks leave the wither DoT, a slowly damaging status effect. Its Q shares the same cast speed as Fire and Water as fastest in the game. Its E and F are not very notable. Its R is very useful, as it has the fastest casting time out of every R and leaves smoke. Its ultimate is quite good and can be used effectively as a counter-ult as it is a very fast casting time.
Water is similar to Shadow. Its Q shares the speed of Shadow and Fire at fastest in the game, and all of it's attacks leave the Soaked effect, which enhances the damage of lightning's attacks and cancels the burn DoT. Its E and F grabs are extremely weak. Its R is very overpowered, being fast to use and even having the power to throw off the aim of projectile attacks. Its ultimate is as fast as Shadow's. The ultimate generates a wave if it hits water, and also deals double damage(?).