If you're looking for a monitor for typical everyday use, you'll find lots of choices at great prices. And finding a wide-screen, 16:9 monitor is not much of a challenge. These types of monitors have all but replaced the squarish 17-inch models. Their width allows for much easier side-by-side page viewing as well as more viewable spreadsheet columns at once, requiring less scrolling.
4K monitors are increasingly becoming available for computers, but they still cost more than conventional displays. They're best for graphics pros looking for a monitor that can show the finest detail. If you're looking for a monitor for more typical everyday use, you'll find lots of choices at great prices.