I have read that 433MHz works better than 868MHz in open spaces such as fields and countryside. An explanation given to me is that 433MHz works like a ground fog and 868MHz tends to bounce off things in cites where it is better suited and can get into holes.
The LoRaWAN and Symphony only seem to be available at the higher frequency. But proprietary protocols are available at 167, 433 and 868MHz these seem to be my only option. Anyway I would appreciate comments.
The company I work for are doing coverage trials with LoRaWAN 868MHz by the way.