People make a lot of those kinds of qualitative statements about sound quality, but when they actually do a rigorous A/B test they usually can't tell the difference.
I've done quite a bit of A/B testing on metal at ~128 kbits and it's very difficult to spot differences on most tracks. Modern lossy audio encoders are very, very good.
Using decent in-ear headphones (I like the Etymotic HF2), listening to Justice, I can definitely without a doubt tell the difference between 128 kbit and +256 kbit. Or more specifically, 128 kbit and lower for specific music makes me feel nauseous.
I'm guessing this type of music simply doesn't compress as well as say... Red Hot Chili Peppers.
I'm not performing a rigorous A/B test, and I can believe that I would fail said A/B test given other conditions (other speakers, other music, etc). I would love for this to be true for all conditions and save all that storage space. Unfortunately, in my personal real-life conditions, better quality does make for a better listening experience.
Are you doing the encoding and performing A/B tests yourself? There are all kinds of things that can hurt audio fidelity a lot worse than bitrate. Some MP3's are poorly encoded by some crappy shareware application. Some are transcoded from an already-lossy source. Some productions will compress better than others (supposedly, some producers actually mix and master with inevitable compression in mind).
My original source was pirated music at 128kbits. Since then, I bought it and have the 320kbit version which immediately sounded incredibly better. Occasionally I'll hear it on 128kibts or 192kbits on Pandora and such, and the difference is very noticeable to me.
My data is purely anecdotal but I feel strongly about it and would be willing to put money where my mouth is if someone wants to call me on it.
Most tracks is not enough. I don't want to lose time fiddling with optimal quality/size ratio per song. 256kbps AAC, clickety click, fits anything and makes a nice, small rip for zero overhead.
Maybe it's a technology difference, but that's the general feel I have across most tracks I've listened to. I'm not A/B testing specifically, but I was complaining about 128 kbit tracks and asking why they sounded empty, even before I knew about bit rates. Systematic Chaos, on 320 for example, sounds amazing.
I'll do some specific testing before I say anything else. :)
Audio perception is highly subject to placeo effect. If you're curious the community at http://www.hydrogenaudio.org/forums/ has worked very hard to make this a more rigorous scientific process.
It's pretty remarkable how good modern lossy encoders are really. I consider it one of the more impressive feats of software engineering of the last decade.
I've done quite a bit of A/B testing on metal at ~128 kbits and it's very difficult to spot differences on most tracks. Modern lossy audio encoders are very, very good.