If you go to www.bmwusa.com and build a Z4 with and without the M sport package, you can see the difference in how the car looks. Better with the M sport, IMO.
2006 525 xi, Orient Blue Metallic, Beige leather, Dark Poplar trim, Premium Package, Cold Weather Package
2012 Z4 35i, ED 2/24/12, Melbourne Red Metallic, Black leather, 6 MT, ///
M Sport, Premium Package, Premium Sound Package, Cold Weather Package, Nav, Comfort Access, Alpine HID Angel Eyes, BMWPedals pedal covers, stubby antenna, Extra Enjoyment Package