There IS a point at which what you really want is a dolly... but even a 12-inch slide can be more visually pronounced than people often assume.
Again it comes down to being a useful tool. If the "pocket size" of the Edelkrone means that you're more likely to HAVE IT WITH YOU then it becomes a highly useful tool.
It really heavily depends on what kind of shooting you do. - If you're in a studio all day then in makes no sense...get a full on dolly. If you have the time and a crew then get a bigger nicer slider... if you're moving FAST or you're stealing shots, then these "pocket" devices are going to be the absolute winners.
Or just sell a kidney and buy one of each!