Infant Onesies or Infant Gowns?

Annie β€’ 23 years old. Diagnosed with PCOS & hypothyroidism. Married for 5 years. Ellie Rose πŸ’•πŸ‘ΆπŸΌ & Millie Jean πŸ’•πŸ€°πŸΌ
What's the best option for a newborn to sleep in?