Besides taking up less space and being easier to use a vertical panel saw is safer to use than a table saw. Table saws are notorious for cutting off fingers or pinching and kicking back a piece of sheet of stock during cutting. On a panel saw, though, you would have to place your hand well under the carriage to cut yourself. This is possible but extremely awkward and difficult to do.
Working in the vertical plane takes up much less floor space. A panel saw can be used when it’s pushed against the wall leaving valuable floor open floor space available. Because of their in-feed and out-feed space requirements table saws are always in the middle of the work area taking up a tremendous amount of space.
Finally, it is much easier to handle and move sheets in the vertical plane – especially the thin flexible materials that sign shops use for many sign blanks, When you pick up a sheet of stock yourself you always carry it vertically.