According to Snowden, Bitcoin does important work and he think it will have enduring value for a long time, but particularly when we look at the core development team and their rate of improvement to the protocol, they simply need to better or they will not be able to compete.
And he is now most interested in privacy-centric cryptocurrencies like Zcash, which obfuscate blockchain data to allow users to verify the integrity of transactions while keeping them private from would-be snoopers.
“When we talk about which cryptocurrencies are interesting to me, I’ve said it before and I’ll say it again, Zcash for me is the most interesting right now, because the privacy properties of it are truly unique, but we see more and more projects that are trying to emulate this and I think this is a positive thing.”
https://www.ccn.com/i-dont-think-bitcoin-will-last-forever-nsa-whistleblower-edward-snowden/