As far as I know you only start talking extended wheel studs when dealing with slip on spacers. The factory wheel studs are designed for a certain wheel centre thickness and factory nut thread length, and adding a spacer on reduces the amount of thread engaged by the nut - can lead to thread stripping etc. if not enough is engaged.

My 2c; get wheels with the offset you're after. Spacers aren't legal unless fitted from factory so it's just another thing that can be picked up if they're noticed. If you have to get them, bolt on hub centric is mechanically better than slip on (still can fail as Dan has pointed out, however.)