Streaming: WiFi or wired??

(1) When possible, do wired.   With few exceptions, in most cases wired will do better than wireless.  
(2) You haven't mentioned a budget.  If this is your entry into streaming, then a Bluesound Node 2i (retails for $550) is a good place to start.          Blu OS is a nice interface.  And it's good value for the money.  

A wired connection will always provide the best connection.  

I'm curious about this "wired always best" attitude. What if someone (like me for example) obtains his or her internet wirelessly to begin with. Is my streaming signal already compromised? 

Or would the wired ethernet still be advantageous coming out of my modem as opposed to wireless?

I'm using a Bluenote Node 2 that somebody miracled me wirelessly and it (including its internal DAC) sounds pretty damn good streaming www.kfjc.org or www.archive.org content.