I noticed that there are large discrepancies between the balances of addresses in Etherscan vs Google Big Query.
Also some addresses that are listed in Etherscan are not existing in the balances table in GBQ. Does anybody know why?
Difficult to know for sure what causes the discrepancies.
In general different nodes may have different information about the blockchain, but this typically last only for a little while for new data. So, assuming that both Etherscan and GBQ have the latest data (why wouldn't they) my best guess is bugs in the systems. An account has certain balance and it shouldn't be possible to misinterpret that, especially for such big services.