working and or mixing at 96k will always sound better.. bottom line.... yes working on music at 44100 using only soft synths that use no samples will sound amazing but when you start to use compressors and eq's at 96k you will notice big time that the over all sum and or mix of your song stands out.... MIXING at 96k provides more precision in getting the sum of your mix to sound more NATURAL.... and then of course when converting down to either cd format and or mp3 from 96k you will notice big time the preservation of the original audio...
mixing at 96k will also provide you with the ability to acquire a higher Master RMS with out sounding over compressed....
another way to create a great sounding mix down is to master your 44100 mix at 96k... bounce your 44100 song down in a stem like fashion ,,, drums, synths, guitars, vocals and so on.. then bring those stems into a new session working at 96k then apply your EQ and compression,,,,that process always yields amazing results....
the science behind HD audio is where the debate seems to be..... audible noise that is organic is HD in nature,, and when organic audio is captured at higher samples rates you are preserving all the frequencies that make up the original sound source,, those other frequencies you can not hear are the frequencies that make the frequencies you can hear sound the way they do..... now,, when producing music from scratch in the DAW,, like with using soft-synths that dont use samples,,, those soft-synths at 44100 are creating audio that is basically already HD ,, even at 44100,,, ... to gain HD audio from samples at 44100 they need to be re sampled and or re recorded at a higher sample rate,,, its a pain staking process but one way to gain HD from non HD samples is to re record the 44100 samples in the analog domain @96k,, and preferably with an outboard processor that can help create new audible characteristics,,, like an EQ and or Compressor.... but even with out using an outboard processor you are creating a fresh new HD recording of that sample and it will for sure be noticed one you start mixing it with any other HD audio that is present in the mix....