Headphones are fine for editing, but if your goal is festivals and similar venues they are not a great option for mixing. The difference between speakers and headphones is moving air. Speakers move a lot of air to get the sound to your ears. With headphones the speakers are 1/2" from your ears; that's the big difference. Another big difference is "spread." There is no way that headphones, since they are covering your ears, can duplicate the sonics of speakers spread many feet apart.
Manufacturers can make all of the extravagant claims that they want. Do you really think that, for only $100, you can have the benefits of tens of thousands of dollars worth of speakers and millions of dollars of mixing venues? How do you know that is what the speakers and venues really sound like? Have you ever mixed there before? So how do you know that it's an accurate representation?
There have been emulation programs by the score in the music biz. Tape saturation plug-ins were rampant ten years ago after the industry moved from analog tape to digital. Even the very expensive plug-ins didn't come close to the real thing. There were a bunch of mic emulation programs as well; use your $300 AKG C1000, insert the plug-in, and it will sound like a $3,500 Neumann U87. Bull crap!!! All they really did was automatically redo the EQ curve; they don't take into account the subtleties of the electronics and air motion - not to mention how the voice or sound interacts with the mic as a whole in real time.
The only emulation programs that have had any real success are the IR (Impulse Response) reverb plug-ins that emulate real spaces. The big difference is that those of us who use them know that we are generating an illusion.