When I was using Firefox I used this extension to unify the address/search bars.
Also Firefox's address bar is much better at searching your history, saving you from doing Google searches. For example you can type the words in the titles of articles you've read and Firefox's AwesomeBar does a good job at suggesting past entries.
This is awesome when you no longer remember the domain or url, but you remember a word or two. In such instances searching on Google doesn't help either.
This feature to me has been an epiphany actually. Google has no interest in developing something like the AwesomeBar, because they'd rather see you doing searches on Google instead.
As far as I can tell, chrome's address-bar behavior is trying to do something like the FF "awesome bar", i.e., combine searches of past urls and titles of pages you've visited, plus google search results, etc., into a single DWIM-like result.
Chrome's results aren't as good as FF's (I typically have to type more to get what what I'm looking for, and the ordering is often not ideal), but it does appear to have similar goals. Chrome used to be much worse at this, but seems to have improved somewhat over time.
As to why exactly FF's results are better, my guess is that it weights the results differently, emphasizing pages you've visited often even if the match is in the middle somewhere, whereas chrome seems to give prefix matches more weight....
[I normally use FF, but use chrome occasionally too...]
Edit: Ah, I suppose the auto-complete is different.