Out of the two I would definately do the Vorsteiner, but personally I would look at the eBay replicas. There are good products out there in the $300 or less range. Just find a reputable eBay seller.
What color is your car? I really like the look of an unpainted carbon fiber spoiler. I think it provides a nice aggressive contrast.
2014 Carrera 2S
- White/2 Tone Espresso/Cognac - Aerokit - PSE - PDCC - SPASM - PDK - Sport Chrono - 20" wheels w/OEM Spacers - Glass Roof - Leather Dash - way too much more to list
2013 E92 M3
- LeMans Blue/Black Novillo - Comp Package - MDCT - CW - PP - EPS - CF Roof w/OEM CF Mirrors, Spoiler, Interior Trim - Full IND package - Muffler Delete