What is the currency conversion for TD Ameritrade?

Just to check as I am comparing the currency conversion rate from Sgd to Usd for my TD Ameritrade account.

From what I found:

• Currency conversion for standard chartered rates are better as compared to DBS remittance (calculator) to TDA.

So will it be better to remit USD from standard chartered directly to TDA account compared to remitting sending SGD from DBS account to TDA direct??