I use the specific one as it also offers historical rates, not all do. With the historical rates your transactions are shown at the US$ price at the time of the transaction so a nice way to see what the transaction was worth in $ back when it was executed.
Thomas
A suggestion - not sure if this is possible but it will be a nice feature if the USD Amount can be included in the data when exporting the history.
I also made a post some time back to ask whether the order of the export file could possibly be changed. Currently the export order is
Transaction_hash, label, confirmations, value, timestamp
Would be nice if it could be changed around to the following:
Timestamp, label, value, (USD Amount), confirmations, transaction_hash
Currently when exporting to a spreadsheet (csv) I always need to rearrange the columns in a more logical order, as above. Not a major problem but would be nice.