To extend Ethernet to remote location, are Powerline extenders or Mesh systems better?

Too bad you committed to an extender... A mesh network is much better for many reasons, not the least of which is throughput: An extender will typically HALF your throughput b/c you're going from one "network" to another. With mesh it's all one network. I got a mesh node and put it in my stereo cabinet in the living room. (The main node is upstairs.) The problem was it generated so much RFI my MC pre-preamp was unusable for LP listening!

So I compromised. I put the mesh node across the room and ran some Cat8 from it to my Node2i. Sounds great! And as could turn off the LEDs on the node, it's practically hidden in the bookcase even though it's in the open. The added benefit is better wifi coverage downstairs for the telly and anything else.

Happy listening...

Doesn’t Roon insist on a wired connection between the box that it is running on and the endpoint? But you can use wifi to control Roon. I think.

I used to use TP link  extenders, but it all was a bit flakey. Some drops. And they used to die at regular intervals.

I am having success with Devolo Magic 2 wireline devices. Seems stable. Roon is happy. Sounds better to me than running the Roon NUC straight into my DAC.

+1 mesh.   A high performance wifi 6 system on 2.4/5G band will work as good as wired if setup properly.   Chose 2.4 if in a low density area like a house or 5 in a higher density area.  
Ethernet over power lines is fine too but has more ways to fail than wifi mesh imo.   It will not affect  your power used for hifi gear.  It’s modulated between 1.5 and 80  mhz.   None of that will ever go through any power supply.   A power supply is an extreme low pass filter :-).  Hifi or not.  
 

I've been using the top of the line TP -Link powerline adapter for a few years now , it's noise free and flat out stable and reliable, it also sounds fantastic.

I did not choose the wifi route.  Currently using a CAT 6 from the router to the streamer.  Can I bypass the router and install a coax to ethernet switch?  What are some things to look for or some good brands?