Funny. I find Safari leaps ahead of Firefox, and even further ahead of Chrome, when it comes to browser performance (CPU use, memory footprint, and especially battery life), with snappier scrolling and animations and fewer weird graphical glitches or mouse/keyboard interaction bugs. For my own browsing habits, Firefox is
very sluggish, and Chrome is completely unusable: it just can’t handle the load and brings my whole computer to a crawl. The Safari user interface also feels much more platform-native and predictable (though it has unfortunately copied several Chrome UI elements in the last few years, which I think make the basic UI worse than ~5 years ago), and I don’t constantly feel like someone is trying to gather and analyze my keystrokes or sell me out to advertisers. (I don’t have a Windows machine, so I couldn’t tell you what IE is like these days.)
Maybe there’s just a focus on different things between vendors: Google has tons of 20%-time engineers pushing new half-baked features in every direction (yes this is a bit of a caricature), while Apple is taking a more measured approach with a focus on performance and reliability.