5-spoke and 6-spoke AMG wheels, what's the difference?
 

Five and six spoke wheels, are there any differences between them in trim and options?

5 spoke are 18 ins; 6 spoke are 17 ins

Not sure about US market but for UK the 17s were standard and the 18s an option; later think they became standard. IMO the 18s are far superior in appearance although the ride may not be so comfortable due to the very low profile tires fitted to keep the rolling radius the same as with 17s.