I am developing (yet another) password manager add-on for Firefox. My add-on needs to:
Jetpack API exposes high level APIs for most of the things you mentioned:
Jetpack based add-ons are restart-less.
Jetpack based add-ons are future proof in a sense that high level APIs will remain unchanged for the coming versions of FF.
You may be able to use some community developed modules for APIs that are not exposed by SDK.
If this is not the last extension you're planning to build there is a potential for code reuse, by building third party modules as ones mentioned in 4 (see docs for details)
Support for mobile FF is coming in post 1.0 version of Addon-SDK which may mean that your extension can be made compatible with mobile version of FF with minimal to zero effort.
Jetpack comes with build-in unit testing framework.
Has a better security model, which will ease add-on review process.
Jetpack support commonjs modules / packages that which means that some of the code can be borrowed from other projects like nodejs for example.