Not even really close. Tower of the helephant by a longstretch due to the first battle being so long and time consuming. When you get to the end, people start quitting because its to hard and long. Not to mention how they cheat.
Well it all depends on how they go - would have to say from word around Helephant tower is worse. Waterworks is more frustration because you maybe in there for gear you may or may not get.
I did both dungeons, and Helephant is hardest. There's so many levels, the first battle takes FOREVER, the last battle is a huge pain because he calls minions who can rebirth, lord, etc.
In the first battle, the partner to the boss will Levy during a period of time, and he does this a lot.
Tower of the Helephant is by far more challenging than Waterworks, imho. Both dungeons share similar challenges in terms of boss rules/cheats, requirements of patience and endurance, and innovative strategies, and both demand exceptional teamwork. I thoroughly enjoy both dungeons for challenge and loot.
However, ToH requires teamwork and serious skills at the very outset; there's no time to get to know the members of a team beforehand. By the time a team gets to Luska in WW, they have spent several battles in getting to know who does what best. There's no margin for error in communication, knowledge of the rules, or deck set up in ToH. Ervin and his pals are an immediate test of preparedness. I absolutely love it!
There's nothing quite like hitting that first boss fight with a group of good friends who are deeply familiar with one another's strengths, strategies, and weaknesses. For example: My sister, Destiny Spiritgiver, specialized in rules/cheats; she runs the show. I specialize in accuracy, power hits, shields, and dispels; I usually sit in Sun spot. Allison Winterblossom tanks, shields, and hits with a devastating Blizzard. David Anvilforge shares lost of blades and shields, and incinerates the enemy; we usually race for Sun spot :) We all wear the life mastery amulet and we all heal. We rarely take new acquaintances in ToH with us, btw. They almost always freak out at the last boss. Hehe...
Anyway, yeah, ToH is the crowning jewel in this wizard's collection. "Liberator of the Helephant" is a mouthful, a well earned one. Oh, and the drops are sweet. I wear the Aureate Band and Lexicon Blade with pride.
Woot woot!
Qbb/Iridian/Scarlet/Moira/Rowan, Liberators of the Helephant
Tower of the Helephant is far worse than Waterworks. Once I do my duty to get the quest done for Tower of Helephant, I'm done with it. I will do Waterworks many many times. Not just for the clothing, but for the practice & experience, plus I like helping others out to get their stuff.