Hmm... Tough call.
The Ender Dragon has a clear mobility advantage over the Warden. It would have Regen through the Ender Crystals, although it's not bodily regen; just HP regen. Problem is given location is a superflat, which is mostly empty AF, the Ender Dragon wouldn't have that. Kinda weird that the wiki doesn't account for macguffin reliance for abilities like regen, tho.
The Warden has everything else going for it. It's attack power is second only to a point-blank Creeper explosion, and it is the most durable mob in the game. It is largely hampered by it being blind, but it does have stereotypical blindness-based enhancements going for it, namely its enhanced sense of hearing and smell. It would give those within a 20-meter radius the Darkness effect, which... Well, apparently it gradually turns into a worse version of the Blindness effect:
https://minecraft.fandom.com/wiki/Darkness
Of course it wouldn't matter to the Ender Dragon since it's immune to all status effects.
Oh, and the Warden has a powerful ranged attack. Here's an excerpt on it from the Minecraft wiki.:
"The warden's melee attack has a cooldown of 0.9 seconds and disables
shields for 5 seconds. If the target is still in its search radius and on high ground or hiding behind walls, a warden can charge up a powerful sonic boom. Specifically, the warden can use the sonic boom if it has been 10 seconds since the warden detects or switches targets, it has been 5 seconds since the warden used a melee or ranged attack, and the target is within the sonic boom attack range of a 15 block horizontal radius and 20 block vertical radius. This guided attack directly attacks the target, passing through
blocks and other mobs without damaging them. The warden takes 1.7 seconds to charge up, then unleashes the attack which instantly hits the target as long as the target is within attack range. The attack takes an additional 1.3 seconds to cool down before the warden can use melee attacks again for a total of 3 seconds. The sonic boom is visible with the formation of green-blue
particles that are quickly projected out of the warden's chest. This attack bypasses shields, armor, enchantments, and even the
wither armor of the
wither. Only the
Resistance effect can reduce this attack's damage."
It oddly enough bypasses most forms of durability, with only the Resistance effect standing a chance against it. Yeah, it has the ability to outright ignore durability; imagine that.
I think the Warden has this myself.
