Western Union's USD to ARS exchange rate tracks the dólar blue. Sometimes it is a little less than the dólar blue and other times it is above the dólar blue. But most of the time the Western Union rate is identical to the dólar blue rate. No matter which currency you are sending to Argentina, your exchange rate will work out to be on parity with the dólar blue. As an example I send AUD to myself in Argentina. The rate I get is the same dólar blue rate I would get if I transferred AUD into USD and then USD to ARS.