Usb or Optical

Have a custom built computer has latest greatest Realtek Audio 1220 vb or whatever its called.  I have a Little Dot Mark ii tube amp and i just bought a SMSL D300 dac.  Should i go optical from computer to desktop dac ? or usb from computer to usb on back of destop dac ?????  im not trying to get dsd or any crazy hi res 24/192 is fine.  Whats going to give me the best sound ?

thanks for all input is welcome.