Melee, for four reasons, from least to most relevant:
1. You don't have to farm resources between every boss fight. Rangers need to keep track of their ammo. As a melee user, I only have to see the ammo counter when I'm fishing.
2. You can always attack the thing you are fighting. Well, at least you can stop that before your first boss. In pre-hardmode, a mage is always having to shoot, then run, shoot, then run, and you get the point. Melee can attack infinitely.
3. It's not annoying. For ranger, you have to aim your shots at least a little well. For mage, the previous is true, but you also have to worry about mana in pre-hardmode. For summoner, well, it's summoner. Summoners rely on AI. Melee, though, is just hit or miss. You hit the enemy, or you don't. No crazy aiming is required, you just walk or fly up and give the boss a huge slap.
4. Projectile swords. It's no secret that melee users love projectile swords. They are definitely awesome. I still try to avoid them or at least also use the blade part, but they are just too cool. They definitely extend my last reason, though:
5. Risk/reward playstyle. Melee users have many choices during a fight. You can fight the enemy head-on with a true melee weapon, or use a projectile to retreat when your health begins to drop. Using melee projectiles to retreat are exactly why the vampire knives are so good. Another good example of risk/reward for melee would be the beetle armor. I prefer the shell, but scale mail is better if you want more damage. I also prefer warding for my accessory modifiers.
Now, the biggest misconception:
WoF being hard for melee: Nope. Even if you don't have an enchanted sword, the weapons you can use have enough DPS to shred the wall, and molten armor is defensive enough to make damage from the boss feel like a tickle.
There are definitely downsides though, such as the flairon being kinda weak compared to other DF drops, and the meowmere deafening anyone in a 50 mile radius. But I love melee, and it is always going to be my main, no matter how many times I get bored of terraria and go back to it.