I probably wouldn't go the other crypto for carrying it around just because bitcoin is the biggest, most famous, and most traded afaik. 

They can only tax what they know about 😉. Although, I believe in some ways governments integrating it makes bitcoin a better store of value than it was. It's more popular and number of fiat you can get for it keeps going up when institutions buy up big.  

 The government does know about the vast majority of it, most people who have bitcoin give their identity to an exchange so they can buy bitcoin.