Everything else being equal, should I expect better Spotify quality through wifi or USB?

kalali: thanks for the response.  I don't have a laptop though.  As I said in my original post, I have a desktop.  Having said that, since you brought it up, should I expect better sound quality through an ethernet cable to DAC or via a wifi stream.  I'll add that I have high speed internet, and the DAC and wireless router will be very close to each other.  If you tell me Ethernet should be better, then I won't look for a DAC that accepts wifi.  If wifi is expected to be better, then I won't look for a DAC with ethernet.  Or I guess I can look for one that accepts wifi, ethernet and usb, and try them all.  I was just thinking someone else may have already tried this and could provide guidance.

Given your set up, I don't think you'll hear a difference between ethernet and wifi and either should sound better than USB given the same quality content. 

It depends on location of Wi-Fi receiver. If it is inside of the DAC then USB and Wi-Fi should be equal since you’re not transferring music but data. USB might inject computer noise into your DAC while Wi-Fi can have dropouts. I had to change my Wi-Fi to 5GHz band because of that.

kijanki.  Great information.  Thank you.  Is there an easy way to tell what band my wifi is operating on?

I use dual band router and dual band receiver (Airport Express).  My router has different IDs for different bands.  On my computer I select one corresponding to 5GHz (can be checked in router setup).  It also depends what do you use as receiver.  Many products, like Airport Express, don't allow direct connection (ad hock) and require router, while others might work direct.