Using my im616 and straight from my 2006 MBP headphone jack, I can tell 10 out of 10 times which is the FLAC.
METHODOLOGY-I used vlc, then clicked randomly on the skip track button with my eyes closed. After AB-ing several times, I can tell which one is cleaner sounding. I only listen to the first 10 seconds or so, and often just the first chord. The first chord has the tendency to sound jagged on the 1st track. After I've made my decision, I open my eyes and then check if I'm right. With the Etys, I chose the same track as the 'cleaner' track every time.
I do NOT have golden ears at all. In fact, when I tried with my fairly newly acquired RE0, I couldn't hear a difference between the two. Not a single difference, and that's considerin I already knew what t look for based on my experience with the im616.
I'm chalking this down to amazing isolation with the ety's and the fact that there is a noisy airconditioner near my laptop.
Though I've recently been enjoying the RE0 more than my im616's, perhaps the fact that I've lived with the im616 daily and for so long means I 'hear' them better.
Maybe something about BAs vs. Dynamics and the way they pick up detail has something to do with it?
Wow. I love this hobby! I learn something new everyday. I didn't think I'd be able to tell the difference with ANY headphone. I have a lot of my music ripped from years ago on a lower bitrate, Am glad I started ripping to higher bitrates when hard drive space got cheaper. :)