What advantage does this have over the cheaper UniFi router in the OP?
The UniFi router depends on you already having a UniFi environment. If you do, it's a good option, but the GL would work with any heterogeneous network
It's available right now, for one.
The Beryl AX is going for cheaper ($70) on Amazon right now vs the UniFi Travel Router ($80). Better bang for the buck on both hardware and software without needing specific Ubiquiti anything.