Butyl patches are typically installed by hand and often have alignment requirements which cause issues on the line. Panel plugs are great alternatives as they're easier to grab (rather than pealing butyl off of a sheet) and they plug in place, preventing misplacement from being an issue.
While panel plugs may not always be as effective for noise reduction compared to butyl patches, they do have great sealing capabilities and water swell resistance.
EPDM panel plugs have great temperature resistance as well as great tensile strength and UV resistance.
A drawback to using molded panel plugs is the added cost of compression/injection molding tooling and the time to make the tools compared to getting production-ready butyl patches. To help speed up this process, Echo uses a proprietary rapid prototyping technology to test and speed up the process.
Accessible Service Points
For panel holes meant as serviceable areas, the best option of the two will be to go with panel plugs due to their ability to be removed and reinstalled.