Higher quality parts will generally be more round and concentric and will sometimes have coatings or better finishing to make them smoother and generally quieter. This would apply to chainrings and cogs. A lot of times rather than just stamping a part out they will CNC machine it so it ups that precision.

Also Dura Ace is well known for being tops and that is never bad for the street credentials. Personally I would like to run a EAI Gold Medal cog and a Sugino Super Zen chainring (on direct drive cranks with a ceramic BB) but the budget isn't so much there, however DA stuff is great quality and works quite nicely on my Langster.