Does the car sound different or anything, or are services just purely to keep ur car running fine?
sometimes your car can sound a bit rough from old oil or lack of oil then when you put fresh oil in it should sound better but apart from that it shouldnt
i dont really think it sounds at all different after a service...if your car wasnt running the best before hand, differences would be more noticeable...
like easier starting, smoother idle, better fuel economy, smoother acceleration...stuff like that.
it may sound different with new oil and a clean air filter if they were blocked, (ive gto a k&n panel filter) but when that gets cleaned (after a few months) it sounds a fair bit different, so im guessing the same if you replace air filter if yours is dirty? but not much