Connecting a streamer via an Ethernet cable

Is there a noticeable difference connecting a streamer directly to an External cable as opposed to WiFi? The reason I ask, is that doing so with my situation would require a fair amount of effort. But if it’s worth it, I’m willing to do it. Thanks.
Ethernet over Power line devices can put a lot of noise into your mains (be especially wary if you are on the same ring main as your system).

That being said I still prefered that and Ethernet cabling over WiFi in my system. Then one of my power line adapters blew and I ran 10m of Ethernet back to my modem and took the powerlines out. This was best of all for me.

Wifi is a good solution if you have no neighbours competing for your channels and a strong internal network. In all other instances ethernet or fibre are preferable. Nevertheless great care needs to be taken to suppress RFI/EMI when using ethernet and on fibre the conversion quality at either end is crucial.
I have a Naim Muso Qb which is all-in-one. It runs 96khz in wireless and 192 wired. So wired matters.  
+ on the Mesh suggestions. I been dealing with this for years as modem on one end of tri level and my main unit on the other with many drywall between. First just a modem/router, then dedicated router then extender finally to Mesh. The first mesh node hard wired to modem and in a position to have line of site to the 2nd node down the hall and all the way to other end of house. 3rd node next to main unit and in line of site of 2nd node. Streamer hard wired to 3rd node. Sounds great and is reliable. The only thing I might do if I want to burn more cash is convert it to optical at the main unit but right now Qobuz rivals CD and my vinyl setup. I is a happy camper.
z32kerber: Why guess? If your streamer supports it, see if packets are being dropped or retried on the WiFi interface, and then plan your strategy based on the data. (for example, if your router is running Linux under the hood, you may need to log in via ssh.)

If necessary, try to improve the performance of your WiFi setup before investing in a  mesh router or running Ethernet cable. The simplest first step is to download a phone or PC app such as "WiFi Analyzer" and use it to find a channel with a low access point count.

Also, make sure your WiFi router is correctly configured. For example, mine had a "smart" feature that was supposed to automatically direct devices to 2.4 or 5 GHz. I turned it off; it wasn't that smart, and would switch bands fairly randomly, causing my streamer to disconnect.

As far as jitter, etc. over WiFi, suffice it to say that people download software (including O/S updates), back up laptops to NAS, edit documents on network storage, etc. via WiFi all the time.

I have no problem reliably streaming Hi-Res Qobuz via WiFi.