The problem with Firefox is not 'speed'. Well, not speed by their definition. The Mozilla team defines 'speed' in the sense of bandwidth: how many operations/second the browser is capable of bringing. This is the wrong definition for most users.
Another very big problem with Firefox is that there is no true separation between tabs. Several times a day it happens that I open a few tabs in the background, only to get Firefox unresponsive due to one of the tabs behaving badly. This is unacceptable. In Google's Chrome tabs are separated to different processes and the browser never becomes unresponsive.
Mozilla should fix the real problems, not some niche geeky problems. If they don't they will continue to loose market share in an alarming rate.
I just compared the two. Firefox 18 was actually slower than Firefox 17 running Sunspider
I can't remember how often the code-generation stage got completely rewritten in the last couple of yours, and now basically they end up with something similar to V8 (developed by google).
For me the big question actually is:
- Why not opt for a clean design in the first place? Compiling dynamically typed languages is not something that has not been there before...
The same basically goes for gecko. Why develop everything by yourself, when you can get it for free elsewhere. Actually gecko's clumsy codebase is the reason why firefox still does not have features like process-per-tab, and why a heavy web-app in one thread can destrroy the browsing experience of another tab (as everything is strictly single-threaded).
However, I still use FireFox as its graphic rendering engine based on Cairo is painting web-pages at light velocity when using intel's SNA drivers =)
There is one major upside to only one process for the browser. It uses a LOT less RAM.
Ok, lets talk about threads. As threads share the same process space, there is no real disadvanatge to use multiple threads - however, Firefox has an inherently single-threaded rendering model/engine.
Using multiple threads would allow multicore-CPUs to shine, and it would reduce the amount of stutter when one tab taxes the CPU,
For me, performance is not the issue. I mean, in a geeky way it is exciting, but that is about it.
I find Chrome extremely frustrating to use due to its tab management, and complete lack of customizability. Not to mention its tendency to use a noticeable more bandwith due to constant pre-cacheing. I also find Chrome uses significantly more processing resources ony my notebook, as much as halving battery life, and hogging all my memory when I need it.