Canonical developers have for some time debated about the adoption of Chromium instead of Firefox, and they seem to have reached an agreement, at least for the upcoming Ubuntu launch, 13.10 (Saucy Salamander).
The debate has been fairly intense and it appeared, for a short time, that Chromium was going to win, at least from the developers' standpoint. The community has been split right down the middle on this issue and no one could concede.
Canonical has now reached a decision, at least for Ubuntu 13.10 (Saucy Salamander), and the issues has been postponed for a little while. The main argument against Chromium seems to be related to how Ubuntu aims to integrate web apps.
“Some great points were raised about the historic pattern of updates around Chromium. First, to get the formalities out the way, Firefox remains the default for 13.10.”
“Second, I'd like to talk about the Chromium issues raised. It was rightly pointed out that there have been issues keeping up with Chromium changes. The big issue was with Web Apps integration and some changing APIs. Since we've introduced Web Apps changes like this have always caused us some grief,” stated Canonical's Jason Warner.
This debate will most likely go on for a while and the decision to ditch Firefox for Chromium will probably be taken for Ubuntu 14.04, which coincidently will be an LTS release.
“Lastly, I do want to consider Chromium by default for 14.04 once the above is no longer an issue. I sincerely believe Chromium is the better experience for general users and should be strongly considered for our next LTS,” Jason Warner ended.
Canonical has stated that Firefox users will not be ignored and the browser from Mozilla will still be installable from the official Ubuntu repositories when the switch is made.