Farrell, ANR is a physical reduction in sound and it is bloody amazing. If you ever get the chance then borrow an ANR headset, but be sure to test it for a decent length of time, not just 2 mins or so because it does sound so different and takes a bit of getting used to. Once tested you will want one - its makes ATC so very clear and noticeably reduces fatigue after a long day.
Warning, don't borrow a friends Bose-x for a 4 sector duty if you can't afford to buy one afterwards like I did! I could only afford a DC10.13 with aftermarket ANR - the sound quality is as good as the Bose but its not quite so light although I find it pretty comfy to wear at work.