Sub-GHz radio is typically achieving larger range in buildings than 2.4 GHz, better transmission through walls and around corners. Also less concurrent services on air.
For this reason, sub-GHz has been often used for home automation and similar purposes. Biggest disadvantage: you need different frequencies for different countries.
Reliable transmission over 30 m can be achieved with less transmitter power in case of doubt. But worst case, 30 m can't be guaranteed inside buildings, neither at sub-GHz or 2.4 GHz.