External wastegate vs. Internal

[DButler]

I am currently setting up a twin turbo and my turbos have internal wastegates. I was thinking of changing them over to external. Is there a benefit of changing these over or should I stay with the internal? If anyone also knows what is required to do this. i know I will need the block off plates, new waste gates, and wastegate tubes. I am under the impression the tubes will mount to the headers. Am I right with all of this? Any help is appreciated. Thanks