After reading the few preceding paragraphs in the previous section, who the winner is should come as no surprise to you. It's definitely FlexBox CSS. Let's summarize this with a list of factors that should be considered when selecting a layout option:

• Browser reach: As developers, we care deeply about the reach of our web applications.
• Ease of use: This one is a bit of a stretch, I know—both Bootstrap's grid and Flex-Layout are built on top of it, making it easier to use. But once you get your head around FlexBox CSS, most layout requirements can be handled fairly easily.
• Ease of maintenance: This one follows from the previous bullet point. But something that most developers are surprised by is the fact that, during the lifespan of a typical application, 20% of the time that developers are involved with it is in building it, whereas 80% of developer time with the application is in maintaining it—and so this last bullet point cannot be overemphasized.

Again, we're not considering Bootstrap and Flex-Layout to be layout techniques because they are tools/frameworks superimposed on top of the underlying layout techniques.