Which engine in the W220

Hello guys, since a buddy of mine still has no internet I ask the question for him here. My buddy wants to buy an S-Class W220. Only with what kind of engine? In question come 320 430s or 500s. How are there about the differences in the maintenance costs consumption etc. It can and should please everyone write his experience with the above mentioned motorizations. Please also tell us what has to be paid attention to when buying. Where are the Mägel in general with the car. Unfortunately I don’t know about the car very well? THANK YOU already in advance for every post. If this has been asked 100 times please don’t be angry.