Personally speaking, concerning real life, it depends on the troop. During Mardi Gras here in Louisiana I like the clean, nice and shiny look. With all the marching we do with Lord Vader it looks really cool. When we are on troops where we are up close and personal, intermingling with people, I think it is a bit cooler to have the worn scuffy look. It adds to the costume, for showing off "damage from battle".
As far as if the empire were real, I think it would depend on where the trooper was. I mean if they were on the Death star or a "clean" environment, then yes the look of the suit would be expected more prim and proper. I think if the trooper was some place like say, Tatooine or Kashyyyk then of course the suits would be more on the beat up side. Concerning what the empire would have as far as acceptable, I think they would take were a trooper was stationed into account. If they were an escort for a superior Lord or even the emperor himself, of course they would want to have the clean suits. But I also think that the empire would know that all troops can't have perfect armor, all the time. (Don't tell Lord Vadar I said that.)