Should I connect my DAC to USB 2 or USB 3?

I use Gustard X12, xmos USB DAC, when I connect via USB 2 port there is 1 zone appear, xmos USB audio 2.0 ST 3033(AISO), but if I connect via USB 3 there is another 1 more zone appear, xmos XS1-U8 MFA(ST), I wonder which USB should I use to get the best sound?