The main issue with the dragon is taking out the end crystals on the towers so it can't regen.
With the recent changes 2 of the towers have iron bars protecting the crystals. Those can be easily destroyed with TNT. I usually put water at the base of the tower so I can jump down after placing the TNT, but sometimes the dragon will destroy the water, so having feather falling boots helps. After that the rest can be handled with a bow and arrows. Once the crystals are gone you can wait until the dragon lands on the exit portal then run underneath and whack away with a sword. A sharp-5 diamond sword (or axe) will do a lot of damage in a short time, and any endermen you accidentally agro will be killed by the dragon while you are under there. Run in from the rear at an angle between the tail and wing.
Also, carry a stack or two of glass bottles to collect dragon's breath. Even if you don't need it, collecting it removes the lingering puddles quickly.
Another option is to use beds. If you can avoid blowing yourself up, it makes quick work of the dragon. Place a bed and maneuver around it to keep the bed between you and the dragon until the dragon makes a low pass at you, then when the dragon is about to pass over the bed, use it (right-click as if you are trying to sleep in it). The bed will go <BOOM!> and deal a whole lot of damage.
I have faced both the wither and Ender Dragon. I was as equipped as you could possibly be for both, and i agree with the majority of you that the wither is harder. While the Ender Dragon is not easy, with the towers and Endermen, the wither is simply more destructive. As i said i was fully equipped and it still would have killed me had it not been for a totem of undying. While there are strategies for the dragon, there is no easy way to fight the wither. It has more health and does more damage, can regenerate, and can become freaking immune to arrows. No contest
also the only way to fight a wither is to spawn one yourself. If you are going to do this and don’t want to die at least once, you will need full diamond armor, sword with smite enchantment, enchanted apples and potions. I would recommend a totem but i know they are very hard to get. I’m sure a lot of you are better fighters than me, but i was as prepared as you can get, and it still almost killed me. If you are planning to fight it in survival mode without cheats, be warned
also they are very destrutive. Spawn it at least several hundred blocked away from anything of importance
make and underground tunnel that’s 1 by 2 so that you can walk through it but the ether can’t. Make a little chamber at the end where you can spawn the wither. Spawn the wither in the chamber than run away it blows up as it spawns it can’t fit through the 1 by 2 tunnel so it will try to blast its way to you. Shoot it full of arrows with the most powerful bow you can make. When it gets to the point where arrows can’t harm it, eat and enchanted apple, them quickly rush out and beat the crap out of it WITH A SWORD ENCHANTED WITH SMITE. this is critical. For best effect take a trentgh 2 potion before going in and use a diamond sword with smite 5. Hit the wither until it dies. If you do it right you should kill it before the regen from the apple runs out, and definetly before the potion wears off. When you kill it get the heck out of there because it blows up again. As for armor, the better the armor the safer you’ll be, so don’t overlook highly enchanted diamond stuff. Protection is the way to go when enchanting.
I have used this strategy 4 times on a withers so i can respawn the Ender Dragon. It works very well.
Also spawn it underground in the overworld, not the nether. That way it can’t knock you into a pool of lava.