I've been to Coachella, EDC, and Hard Day of the Dead and I can say I think I had the most fun at Hard Summer or at least got the most for my money. There were no lines at all. Some of the friendliest concert goers I have ever been around. All of the stages were very cool and well separated. If you're a fan of any type of electronic music (besides trance) Hard had it this year. There were HUGE names such as Knife Party, Dog Blood, Flux Pavillion, Disclosure, Kill Noise, Duck Sauce, Tommy Trash, RL Grime & Clockwork (separate shows!), Empire of the Sun, Zedd, Bassnectar, Crystal Castles, Dillon Francis, 2 Chainz, Flosstradamus, Baauer, Justice, Gesaffelstein, and many more all in 2 days. Everyone I know saw at least several shows that really blew their mind. For me it was Flosstradamus, Flux Pavillion, Knife Party, and Dillon Francis.
The only thing I wish was different was the start and end times. No one wants to go to a rave during the day. The atmosphere is just so much better at night.