what a terrible dilema!
actually i had this same problem a few years ago.i was trying to decide between a 2yr old 740 or a 3 1/2 yr old s500.i guess you have to ask yourself what you want out of the car.performance,luxury,style,grace,roominess and resale.they both have these qualities to different degrees and usually some come at expense of the others.my primary issue was space for the wife and three growing boys(and boy are they growing!)when i realized that hump in the back of the 740 was going to be a problem the benz choice was obvious.also i think the s500 is more prestigious compared to the 740-but that's my opinion.