I’ll preface this by saying that I’m not here to convince anyone of anything. The best solution is the one that meets your needs best and we’re all different that way. I’m merely offering another perspective for any other reader who would be interested in, before they arrive at their decision to go whichever way.
The reason for my decision to use Volumio over Chromecast, I’m simply tired of major manufacturers dictating when it is time to upgrade hardware in a regular and wasteful manner. Whether it is an all 'round media player or a dedicated audio player, I don’t want to have to change my hardware every few years to support the next iteration of software or OS required to drive that software. For example, I use my phones until they drop dead and I can’t repair them any further. I build computers that will last me for at least six years before I need to consider an upgrade.
In the media space, it just got tiresome after the second Android box.
In the audio space, it got very tiresome after all the money I spent on a nice looking Denon DNP-720AE for simply playing my FLACs, only to have its firmware support go down the toilet in typical Denon style, while the overall features fell way behind the rest of the market’s advancements not long after.
Since then, I’ve been attracted to open source ecosystems and Volumio fits the bill for me very nicely. My seven year old Denon amp supplies the power to a Raspberry Pi via its USB interface, I feed the audio into the amp via SPDIF and Volumio is tapped into my NFS share on my NAS.
Turn on the amp, Volumio is already running because the Denon USB is always on even in standby, call up my interface on the phone or PC, browse, play, add to playlist on the fly, etc. It fits my simple needs beautifully. I don’t care for voice commands, I’m happy to use my fingers and aside from my smartphone, I don’t want to add any more spy devices to my ecosystem.
With the ongoing development work that the guys are putting into Volumio, I’m confident that I’ll have a product that will move along with the times without having to shell out for new hardware every couple of years. I’m not a tree-hugging hippie but I am a fan of not being so wasteful.
Hopefully that helps any reader still sitting on the fence. At the end of the day, try them both and be your own judge. Only you know what you need for a satisfactory result.