1. Hubbub provides a SAX-style (callback-based) API, while Gumbo gives you a DOM-style (tree-based) struct directly. Hubbub is likely faster in this regard, Gumbo is easier to use out-of-the-box.
2. Gumbo is better tested. It's unclear whether Hubbub's 90% test coverage is "90% of the code is tested" or "90% of the tests pass", but Gumbo has 100% code coverage, 100% of html5lib tests pass (as of 0.95; the html5lib maintainer has pointed out that additional tests were added to trunk recently that don't pass), and it's run without crashing on ~4.5B documents from Google's index.
3. Gumbo has better support for source locations and going between original text and parse tree.
4. Hubbub has character encoding detection, Gumbo doesn't.
1. Hubbub provides a SAX-style (callback-based) API, while Gumbo gives you a DOM-style (tree-based) struct directly. Hubbub is likely faster in this regard, Gumbo is easier to use out-of-the-box.
2. Gumbo is better tested. It's unclear whether Hubbub's 90% test coverage is "90% of the code is tested" or "90% of the tests pass", but Gumbo has 100% code coverage, 100% of html5lib tests pass (as of 0.95; the html5lib maintainer has pointed out that additional tests were added to trunk recently that don't pass), and it's run without crashing on ~4.5B documents from Google's index.
3. Gumbo has better support for source locations and going between original text and parse tree.
4. Hubbub has character encoding detection, Gumbo doesn't.