Sonos has said the Windows app will be cancelled after the current problems are over. It has been technically laid to rest for a long time and just kept ticking over to keep in touch with newer software on the speakers. Keeping it updated will not make things worse because of this, it might make them a little better because it will keep up with the speakers better.
The only problem with the newer firmware is the mis-indexing of compilation albums, which has no work-around. (There are also issues with device discovery, but harder to quantify).
The only problem with the Desktop app is the change to the setup of local music sharing, which has had multiple fixes and documented work-arounds.
These are minor issues compared to the gigantic problems with the new app.
I would stick with what you have if its working for you.