MAC Upsampling - to upsample or not?

[Opusover21]

Appologies if this is a repeat. I've read conflicting views on using the midi panel in Mac OX. I personally leave the sampling rate at its highest level which using the Weiss DAC2 is 192khz...What advantage is there playing the files at their native resolution? whats wrong with the upsampling on the Mac? Can people spot the difference playing a 44.1 recording and then upsampling it via the Mac? I must admit I'm struggling to hear the difference on my Mac mini/Weiss/Valve/QUAD 2805 system...

 

Any thoughts?