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, LED Angel Eyes, BMWPedals pedal covers, stubby antenna, Luxon strut bar, CF engine cover, LCI side marker, powder coated calipers, Extra Enjoyment Package