Regarding FM onm the Xperia :
currently Sailfish 2.2.0 doesn't have a functionnal driver, according to Jolla's announcements.
(There's no /dev/...blah... showing up to play radio with).

Maybe they'll manage to activate the functionality in a future kernel.

If you absolutely rely on radio musique, but can at least get a good connection ( either Wifi or 3G/4G), consider using web radios in the meantime.

Sailfish is, in my opinion, a good solution if you don't mind getting your hands dirty and hack and tweak stuff here and there.
While at the same time you still have some access to Android and don't miss the applications that you might be needing.

Beware, the current Android compatibility has very little direct hardware access. e.g.: It can't directly drive Bluetooth devices.
So forget using an Android app that talks directly to your sport health monitor gadget.
Sailfish has some bluetooth support, so it can handle some devices (e.g.: Bluetooth speakers), which will then show as generic audio output to the android apps. You can thus still listen to musique with Spotify on your bluetooth speakers.

By the time of Sailfish 3.0, Jolla might be considering some better solution, but aren't allowed to speak about it yet.