I've used both. The Bose is slightly more comfortable and offers more (or more obvious) noise cancellation, ie when you flick the switch on the Bose it's like someone's stuck your head in a plumber's plunger. 'Better' sound quality, if you like the Bose sound (I don't).

OTOH the EK one doesn't need batteries, works as normal headphones when the noise cancellation is switched off, and the cable is more sturdy. But you sometimes have to give it back half hour or so before landing.

I own and use a set of custom in-ear monitors which I use pretty much from boarding to landing.