It would be irresponsible to discuss Mirapex (pramipexole) and ReQuip (ropinirole) in terms of a competition. If you are living with Parkinson's you should be considering whether or not an agonist would be beneficial to you. If you and your doctor suspect that therapy with an agonist would help you, then you need to ask which one matches your needs best.
Certainly one is more popular than the other, generally. However, there is no such thing as a general person with Parkinson's. PD manifests itself differently in each person. Both Mirapex and ReQuip offer robust benefits to the right patient at the right time.
One strategy is to use an agonist, rather than levodopa replacement therapy, to address early PD symptoms. The lengh of time a dose of levodopa works decreases after a few years of use. Using an agonist allows a person to "save" their levodopa resistance for a few years.
Dr. Warren Olanow, a New York neurologist explains this strategy toward the end of this movie. This strategy is not perfect, however. There is evidence that delaying therapy with levodopa has negative consequences. You and your doctor can decide how important and agonist may be for you, and which one is ideal for your situation.