I came across this research paper comparing 433 vs 868 MHz for LoRa. Surprisingly, it turns out that 868 MHz works better in terms of packet delivery.
I recommend everyone to read this paper once. They have interesting data in there.
This PDF link might not work in the future, so for readers reading this far in the future, search Google for “Study of LoRa Performance at 433 MHz and 868 MHz Bands Inside a Multistory Building” or SciHub is your friend