Streaming: WiFi or wired??

I just ran a test the other day.
My DSL modem can be connected with an ethernet cable, or switched on to run WiFi.
I made two video files downloaded from the internet.

The WiFi was not as precise and clear. The copper wire download was clear and the sound was better. But, you should get better quality ethernet cabling for the best sound.

If you are going to stream hard wire using CAT6.  Otherwise you will get signal breakup.

I'll second larry's notion on CAT6. I have a new Node2i that I started with wifi. The setup was a challenge.  For networking reasons, I moved my router from another floor to the stereo cabinet in my lair. When I hooked up the provided ethernet cable, I was impressed with a lower noise floor, etc. And there was no setup.
Upgraded to AQ Pearl and am like a pig in mud.

Anyone believing they're getting "better" or "clearer" SQ from wired vs wireless ethernet (or vice versa) has fallen into one of those confirmation bias traps we humans are prone to falling into.

Empirically and physically THERE IS NO DIFFERENCE in the final correct and intended data received by an ethernet network endpoint, whether wired or wireless. IT's IDENTICAL if the associated networks are performant. Read @cakyol's replies above then read up on tcp/ip, application protocols and the OSI network stack model.

ps: and all those snake-oil peddlers of "audiophile" network gear? Best-case is they don't understand ethernet network science, and are running their businesses for the usual reasons. Worst-case is they do understand ethernet network science - and are running their businesses for the usual reasons + engaging it with less-than-honest intent.

Yes.  Don't believe your lyin' ears!