Checked Sumatrapdf on Windows and it's better - while on some fast mouse wheel scrolling the web version is more responsive, but then it doesn't adjust text quality, so shows blurry version (though zooming seems to fix it) while the local versionalways shows high quality text (sometimes after a delay)
Pageup/down scroll is without a delay locally but it scrolls through blank pages, so I guess mouse scroll just always does quality rendering, thus it's the only operation that's slower locally
So while pages load faster in the web version, they are of much worse quality initially