Hi,
Since the seats keep filling with each round, the competition naturally increases towards the end. There are two factors to consider here - the readiness of your application and the application window you are in.
If your application is 90% ready and you are in R1, finalize and submit. However, if almost 40% or so is remaining, you are better off taking more time and applying for the next round. If the B-school has 5-6 rounds there will not be a major difference between R2 and R3. Try to avoid applying in the last round.
If you are an international student, it's also important to apply early as it will give you more time to get your visa process approved and your travel arrangements in order, post a successful admit.
To know more about this you can now visit
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Intelligent B-School Selector Tool for a better evaluation.