Hi there, my friend! Generally speaking, schools will always keep a certain quota of enrollment for each round. Keeping that in mind, there are two pieces of advice for you:
First, aim for the first round. It’s always better to prepare and apply early. This will show that you have a long-term plan and are able to stick with the plan. Also this can express your interest and passion for the school and being willing to commit.
Second, it reeeeeally depends on you which round to apply. Evaluate your preparation and schedule. If you are not ready for the first round, don’t rush it. Show the BEST side of yourself. Especially for MIT or Vandy level schools, you definitely need more time to prepare.
Finally, don’t try to go with the “easy round”. The only thing you can control is your own application.