Well, since I am a huge audio fan I decided to do a comparison before and after the update. I captured the audio using a mic into my soundcard of my PC and set the mic up 3 inches from the speakerphone of my iPhone 5 (no case on iphone so nothing to block sound. I actually did 2 tests before and after the software update. Here is what I did:
Tested Before 6.1.4 software update, iPhone sound at 75% volume
Tested Before 6.1.4 software update, iPhone sound 100% volume
Then installed update
Tested After 6.1.4 software update, iPhone sound at 75% volume
Tested After 6.1.4 software update, iPhone sound 100% volume
My findings:
I used the same 45 second clip of a song in my itunes library on my iphone 5 to do the comparison, recording it each time separately for each listed above.
It was hard to tell the difference much when at the 75% volume. However when listening to each at the 100% volume level before and after the update, I can tell after the update that the sound is just a tad better, it has less of a tiny sound, slightly fuller, there is a spot in the song when at the 100 level I can tell it vibrates a bit more before the update and after in the same spot on that song it sounds better controlled, the reason I say it sounds a bit fuller and a bit less distortion.
So I would say the update a tad better when listening to music at 100%. I would also say it's going to sound better when watching music videos and such at 100% too.