ARDL can be used for checking for co-integration if you have a mix of I(0) and I(1) variables. The Johansen's method requires all variables to I(1). Please see Prof. David E. GIles blog for excellent illustrations. (http://davegiles.blogspot.in/)
In addition to points mentioned by Arun Vishnu Kumar, ARDL is preferable when your sample size is small. You can refer to the article attached herewith.
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The two above answers are correct. It is better to use ARDL method when your sample size is small; and you have to use it if your data is I(0) and I(1).