Yeah it's nuts I've never really been a music festival person, my ex talked me into going and I'm glad I did. It's definitely a surreal once in a lifetime experience. We ended up scoring artist passes for EDC so we were just backstage the whole time at the different stages, people were wondering who I was the whole time.
Ultra in Miami was sick, Steve Angello stayed at the same hotel as I did (W in south beach), it was pretty badass I pulled up to check in and I saw Alec Monopoly's Rolls Royce Ghost and Steve Angelo's Rolls Royce Phantom parked next to each other and I knew it was gonna be a sick trip.
EDC overall was a better experience as far as the festival itself went, but Ultra was just so much sicker in general because of the whole experience outside the festival I got to meet and party with so many artists. Skrillex ended up hanging out at my VIP booth at a club called E11even and a couple friends ended up crashing at Datsik's place and I got to meet him the next day and hang out for a bit.
I would recommend going to both if you get the opportunity, I'm definitely going to both every year I can from now on.
Not to derail the OP's thread but basically yeah, agreed with OP, it's hard to beat EDM concerts & festivals as far as fun goes. It's always a good time.