[kevingadd]

Scroll latency has nothing to do with performance. You can achieve low scroll latency by doing scrolling and composition on a worker thread - which, IIRC, is more or less what OS X and iOS do, and is something Safari can take advantage of freely because it's not portable.

If memory serves, recent builds of Firefox (on the non-release channels) are actually starting to roll out OMTC (off main thread compositing) which delivers the same sort of 'performance' you like about Safari, while keeping the perks of Firefox having a faster parser, faster JS runtime, and modern feature set.

You are generally correct that latency is important, though. I don't know if the Chrome dev team prioritizes it much, but Mozilla recently started putting more effort into measuring and reducing latency in various parts of the browser (inattention had let latencies get pretty bad in some places.)

Safari's fortunes aren't tied to advertising because Apple already extracted a payment for every user that runs Safari. They're free to do those things like disable cookies and bundle an ad blocker because they don't have to consider the desires of content creators or generate a revenue stream via their browser. It's the same set of tactics Microsoft was free to use with IE. It's impossible for Firefox or Chrome to offer similar features without directly undermining their revenue sources.

[zimpenfish]

Scroll latency has a lot to do with "perceived performance" and that's the only measure a user cares for - Chrome might be 1000x faster for SunSpider / whatnot benchmark but if it stutters and stalls when scrolling a page, users will consider it slower.

[kevingadd]

If in one browser an asm.js compiled Unreal Engine 4 game loads in 5 seconds, and in Safari it loads in 2 minutes, you better believe users will notice. JS performance matters.

[zimpenfish]

Yes, they'd notice that. But how often does that scenario (running Unreal Engine 4 under asm.js) happen, would you say, on a day to day basis? Compared with trying to scroll a loading webpage, I mean. We're probably talking orders of magnitude difference, I suspect.