Maintenance testing vs testing a new system

What is the difference between testing existing systems and new systems, considering test types, triggers for testing and amount of testing?

Test types are the same: confirmation and regression testing. Confirmation testing is performed on the changed software, whereas regression testing serves to demonstrate that the changed software works as intended.

Triggers for testing differ: in the case of maintenance testing it's modification, migration or retirement. For testing a new system the trigger it is delivering a functional from the user perspective product.

Amount of testing is bigger for testing a new system, as for maintenance testing the amount of regression testing can be optimized due to the impact analysis.

I feel like I'm missing something, as there should be some other differences.