i'm not too concerned with the look but more of a safety reliability issue. if this single arm fails on the highway during the winter with the spray of cars infront of you...you can really be up the creek very quickly. at least with two wiper arms you have a backup...assuming it fails on the driver side. sure mechanically both maybe attached to same motor but it is still a backup.
and given it's from ebay - i'm not sure quality is up to snuff.
reliability aside there is also practical use of it...i'm sure it doesn't wipe up to the corners like the MB single arm does. if it sweeps as a full arch you are left with big corners left untouched.
looks are one thing..but if it compromises safety....your call at end of day