SoSim is like 33 per month for their 50/60 GB data and 5000 minutes. If you sign up for the annual VoLTE package, you basically get unlimited voice minutes at approx ~6 per month. Another $5 for the voice mail and you're still looking at a sub $50 price for more data than you can use casually (unless you're tethering or using as home wifi, which is a separate topic).
The only place Birdie seems to be better is that they offer the roaming day passes to multiple destinations, whereas SoSim only has it for the Mainland, Macau and Taiwan. Apart from that, Birdie also offers VoWiFi, not that HK has too many dead zones when it comes to mobile signal coverage.
Speaking of VoWiFi, has anyone tried using it on a local SIM when abroad? Does it act like a local number when connected to a WiFi network? I know that AT&T and T-Mobile numbers with VoWiFi can be used abroad as local American numbers to make and receive calls while connected to WiFi while staying in airplane mode for the cellular network.