I'll just add to some similar answers but emphasize that if you really want to maintain a very sharp edge, don't use a ridged steel. At best, they'll take a slightly dull knife and rip some microserrations in it that will make it temporarily seem sharper, but those microserrations will gradually weaken the edge and require more in-depth sharpening to be performed sooner. At worst, a ridged steel can put larger chips into your edge, which will make subsequent sharpening even harder to do.
This is partly a personal opinion, but ridged steels are common and people buy them because they are more interested in making a knife work a bit better when it begins to dull, rather than doing maintenance to keep knives really sharp consistently.
A smooth steel is better for honing, as it will just take a curled edge and straighten it, which is all you usually want to do with a truly sharp knife. Eventually the edge will begin to weaken with use, so a very fine grit ceramic rod can be used to touch up an edge (and pull off weak bits without creating a lot of jagged microserrations) if you don't want to pull out the sharpening stones.
As noted in another answer, one can usually recover from poor honing even with a ridged steel by taking the knife to be professionally sharpened (or learning to do it yourself). But harsh honing with a ridged steel is not without its costs. Subsequent sharpening will require more of the blade to be removed to return the knife to a fine edge. And with German style knives that generally have a full bolster, this can quickly lead to hollowing of the edge near the bolster, meaning that the knife will not make complete contact with the work surface. That means you need to grind down the bolster, which is more involved that simply pulling out a sharpening stone.