R171, which engine 350 or 350 sports motor

Sorry to interrupt again. Since there is hardly any offer from the SLK AMG55 R171 and then mostly Japan reimports which have already been evaluated here and made recommendations. I am now looking at the superior in the direction 350 or 350 sport motor. Question, which engine would the experts prefer here. Unfortunately my color is silver and so I found a few SLk350 which have about 55 thousand km on the speedometer and from 2005 to 2007 are then 2 with sport motor both 2010 g ebaut. One with 10.tkm one with 51tkm, private sale and around 23000€, the question arises, the price is not a bit excessive. This choice is also not very nice. It would be very friendly to get well-founded opinions here. Or should I practice in patience and see if what comes after. beautiful Easter still…