The image below is the Roboto Slab font as rendered by Chrome and Firefox. The same text is shown using the same font-face, font-size, and font-weight and yet they look slightly different. Chrome shows a slightly thinner font while Firefox has a thicker font and has somewhat more even lines.
Which one is more readable? The thinner lines on Chrome looks weaker but easier on the eyes while Firefox lines looks stronger and is readable even when read from further away. I prefer Firefox slightly as it displays the difference between different fonts more clearly. I think using various fonts in a page would end up looking similar in Chrome unless they are not of the same style — serif and sans-serif.