Fat zebras have less visual noise because they switch back and forth less frequently. As for tracking, I find them even easier, simply following the top, middle, or bottom row of the filled section across. (We will have to wait for a follow-up study to see if they actually help – it seems people don’t prefer the look of them on smaller tables, but there is no indication on their performance.)
One potential drawback to consider when using fat zebras is ‘implied grouping’. Depending on your data set, people may think the fill colours indicate that data share some specific quality. For this reason, it is vitally important, as with regular stripes, that the background fill be as subtle as possible. I would also recommend avoiding it when there are only a few rows of data visible as it’s even more likely to appear as data grouping.
Edward Tufte claims that “good typography can always organize a table, no stripes needed.” When working with large tables, however, I prefer to show my stripes, even if they are fat.
