Just wondering, one is 8MB (Mozilla Firefox) and the other is 28MB (Apple Safari).
Why is there so much difference in the size of these browsers?
The Apple application bundles a lot of software which is meant to support other Apple products such as the iPhone and iTunes. If you break the installation file up using Universal Extractor, you can see the bloat.
Among the products that Apple installs are the very annoying Apple Software Update and Bonjour. In addition, it includes two versions in the installation file: both 32-bits and 64-bits.
Mozilla Firefox installs just one 32-bits browser, and with a minimal number of add-ons. It has no aspirations to being a platform. It's just a browser.
This is one of the reasons that I haven't considered Safari as a browser alternative to Firefox.