I have been thinking a lot recently about different layout methods in CSS. I was fortunate enough to start doing web development in a time when there are tons of options for layout.
Set up properly, these kinds of grids are easy to work with. Floats are supported in practically all browsers, making float-based grids useful when backwards compatibility is essential to your project.
However, using float to make a grid is not intuitive. These grids require clearing context, pseudo content, and your code can get unwieldy if you need grids for several screen widths.
I had some prior experience with CSS Grid, but had never used Flexbox before. I found this excellent tutorial from Chris Coyier at CSS-Tricks on using Flexbox to make responsive grids. Using Flexbox in my current project, I cut the amount of CSS devoted to layout down by over 50%. Layout with Flexbox is so easy, and the CSS is so clean, that I am kicking myself for not learning Flexbox sooner.