To me, any grid is an afterthought to a map design. You first create the kind of detailed map you want. When you're done you place your grid whatever that might be - square or hex. To me, creating the hexagons first as backwards design - why would anyone do that? Now if you're using an application like Hexagrapher, a hex based CAD drawing system, then that's how the designs are created. Maps I create can easily have square, hex or no grid, because as I stated grids are something I do as the very last thing in any map design - it really is only an afterthought.