Ems are more versatile. When increasing the size of all fonts at a particular breakpoint for instance. Instead of having to adjust each font-size property individually you can simply change the font-size of the root element.
I read your article. But i am still wondering why you cant shift the pattern so that the lines really line up with the baseline. You can influence the leading via margin or padding and the line-height property, right?
Absolutely, you can hack it on a very individual basis, but this introduces some major problems. For instance, browsers and operating systems all render fonts differently, and as the web is fluid by nature, simply having a sentence break to the next line can be an issue. Also, it can be incredibly different based on the typefaces you are using.
then i still don't get it. When a simple line break would break a horizontal baseline-aligned grid, wouldn't it break a horizontal baseline-plus-some-space-aligned grid?
Although the css prop. "line-heigt" is not implemented in a convenient way, it is still deterministic as I understand from the quoted article:
"This is determined by working out the difference between the line-height and the font-size, dividing by 2, and then placing the calculated amount of space above and below each line of text."
Opera on my phone automatically zooms whenever you tap a link near another link so you can select with no ambiguity, and I believe Chrome on Android does too:
Safari is notably lagging behind but it's a crappy browser... back button right next to the close tab button suffering from the exact problem you're describing.