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

I am just not sure what conections you are really comparing. A (wired?) computer with a usb cable into a usb DAC I understand and should give excellent results. Unlike some believe computers are an excellent source, and usb to an external DAC is fine. But how does your alternative actually look like?

The 2 choices I am looking at are:

1) USB out of desktop computer into DAC
2) Wifi connection to DAC

I am wondering if there would be any difference in streaming Spotify sound quality between these 2 options, using something like a Bluesound Node 2, which can work with either option.

Same DAC? The DAC may have a very small sonic signature (but not much). If the rest is functioning properly, it is highly unlikelely there will be a sonic signature from that part of the chain.

willemj: Did you read my original post?  Yes, same DAC.  My question is written:

If the DAC, amp, speakers are the same, will one of these 2 options likely provide better sound quality?

Sorry I overlooked the 'same DAC'. If I understand you now, this is a DAC with both a usb port and a streaming facility, or, to put it the other way around,  a streamer with its own DAC. I would be surprised if there are any sonic differences, so I would go for the most convenient option.