I think it can work two ways, for and against us.
1) imagine a plain van drivng around at the wee hours of the morning, suspiciously driving around a neighborhood trying to look for the shipper/consignee, but the police/public doesnt know he is an expeditor.He could be mistaken for anything.Stickers give the police/public an idea he is a delivery company,eliminating many possibilities and situations are avoided.Decals are for us in this way of thinking.
2) Being pulled over/in scales by a dot officer, who may mis interpret the dot rules and regulations of what is and what is not considered a cmv can hurt and be against a van at this point.Aplain van may not be messed with as much in this case.Decals are against us in this situation.