Personal opinion: Beating Beat Saber as a workout program (as much of “not a workout program” as it is) is going to be really tough - Beat Saber is fun. Most workout programs, be they games or with a trainer... aren’t.
Both are beat games. The most obvious way to see the difference between them is to watch someone else playing each. One game looks like someone dancing around and trying to look cool, the other looks like a robot being short circuited.
If you have experience with Beat Saber you can go straight in at expert modes in Synth Rider (e.g. level 4 or 5).
SR is also more like a puzzle game for me, there are certain songs where you have to figure out what kind of dance moves would make it physically possible to complete the track perfectly, how you could modify them to get more points etc.
No connection to the developers of either game, and both are worth owning.
That's why I started this, to try and create something that does the maximum of physical workout (in terms of body parts that are used) that I could squeeze out of the VR gameplay while still making it entertaining.
So I am coming at it from the opposite direction beat saber does.
Fun music game that is also physically engaging <-vs-> Physically intensive game that is also somewhat fun