I've had at least 5 Fusion stereos and never had any issues with them failing. While I like the Fusion integration options with MFDs, I have found that to be a nice-to-have feature, as it doesn't work anywhere near as well as a wired remote, or using Fusion-Link apps on smartphones/devices.
However, I 100% agree that Sonos sounds far better, and is generally easier to upgrade to as long as you have 120VAC available. I have Sonos at home, at a vacation house, and on the boat as well. Not only does it sound amazing, but you can tune it for each room with an iPhone so it sounds appropriate. In addition, guests, provided that they are on your WiFi network, can add songs to the queue, contribute their horrible music, and generally have fun.
We have two Play 1's in the salon along with a subwoofer, and it is the loudest, most clear and dynamic sound I've ever had on the boat. There's also a Play 1 in each stateroom, which is pretty overkill but still nice when retired for the day/night.
I plan on adding a Beam, which is a sound bar, for the TV in the Salon, and removing one or both of the Play 1's there. The Beam has Alexa, so I can yell at it to play things while around the cabin, which should be nice. That combined with the Subwoofer should be more than enough for both TV and audio in that room.
I've been toying with the idea of a Play 1 at the flybrige, but I also have a Fusion radio installed aboard as well with speakers in the Salon and Flybridge. They just can't keep up with the quality of Sonos....