Just as using a device "wired" vs "wireless" is better because wireless in the mix adds issues not found using straight wire connections. So yes, wired is better than BT, in most cases, but then the portability of the sound is important, too. Most BT speakers have no adjustable volume, but then my wired connection of Dot to stereo has none either except with the stereo volume control. So, I have the Dot at a volume level that matches all the volume levels of other devices and do not use Dot to do all the volume adjusting connected to stereo, we use the master volume control of the stereo.
This is not to say do one or the other; just understand what can cause any volume differences for best results.