What's the difference between 帐户 and 账户? To my understanding, both mean "account", as in a bank account or online account. 账户 also appears to be the more common (100M search results) compared to 帐户 (about 50M results). What is the difference, if any, between their usage and meaning?

To boot, they have the exact same pronunciation.
账户 is the correct form, and 帐户 is a common typo seen a lot in online services. 

账 or 账本 means "books", and 记账 is the action of "accounting". The word 账户 means a "bank account", and is also used as "online account" nowadays. 

帐 has meanings related to cloth, like "mosquito net"(蚊帐) or "tent"(帐篷). 

P.S. There is no entry for 帐户 in The Standard Dictionary of Contemporary Chinese.