Writeup is up, this is the most detailed page anywhere on the VW mirrors. Applies only to mk4 and mk5 cars.
You have 3 choices, flat like your drivers side for a stock replacement, convex like your passenger side (but on the driver's side) or aspherical, which is convex with a super wide outer section to really see into your blind spot.
The reason why you might want a stock flat mirror is because you don't want a blind spot mirror because it's not a DOT approved part and because objects are closer than they appear, making it harder to judge distances.
The heater in the stock mirror also burns out. The power mirror switch has to be left in L or R, the middle position is HEAT. As a result, most people's heated mirrors are burnt out.