Easy to buy/sell tBill at Fidelity while TD can only buy

The key difference is at Fidelity you can buy at $1k increment and sell on open market any time before maturity. At TD you can buy at $100 increment only to maturity: if you want to sell before maturity you have to transfer to any brokerage to sell; also TD website security is very restrictive, much harder to contact customer service to resovle any issue.