What Firefox has:
1) the Awesomebar, which I love, although some people hate, plus more advanced functionality -- like in Chrome you can't search your history and delete items in the search results, which I think is retarded as your only option is to purge your entire history
It also seems pretty clear that Chrome is built to use the Google Search Engine whenever possible. For example if you search for something in the location bar, Firefox can redirect you to the very first result on Google for that search if it has a high degree of certainty. The Awesomebar is also designed such that you'll do less searching on Google.
However, the ties of Chrome to Google can be seen by the way the browser makes you search on Google, even in cases where a local search in your history would make much more sense.
2) Firefox plugins can do pretty much anything -- Chrome plugins are basically useless. I.e. Firebug can be a Firefox plugin, while on Chrome this had to be baked in. It means Firefox can have things like proper ad-blocking and Delicious integration on the push of a button
3) a non-profit organization behind it -- when dealing with companies and organizations the concept of "trust" applies heavily, and personally I trust that Mozilla looks after my interests much more than I trust Google