I have two WiiM Pros, both running off Ethernet. One is upstairs and would have great WiFi, but Ethernet was handy. In the basement, particularly the little alcove where my electronics workbench sits, WiFi is pretty weak.
WiiM Pro wins over RasPi/Volumio for me because Volumio requires a subscription for advanced features that WiiM includes.
WiiM's app needs improvement, in my opinion. I can't navigate to a folder containing a multi-disc album and play in disc>song order. It wants to play disc1-song1, disc2-song1, disc3-song1, disc1-song2, etc. A playlist of the folder in correct sequence would halt after about 14 songs. Makes it difficult to follow a concept album. Maybe it's changed by now. I've found BubbleUPnP works better for selecting and playing music, yet the WiiM app is necessary for managing the hardware.
In spite of the frustration of maintaining two apps for one device, I still prefer the WiiM.