Basically, they share the same functions. The difference is the service go with Premium package, it is much more than startup package. Please see details at pricing page. They share the same first payment, but different in renewal payment

Startup package price means first payment $179.69. After the first 6 month, you will need to pay $39.99 to renew next 6 months, or it will be limited in feature when it expires

While Premium package, the first payment is $179.69. After first month, you will need to pay $59 monthly to renew or it will be limited in feature when it expires

Renewal will grant download, update, support as well as keeping your plugin as Premium version.