Get the 530i for two simple reasons:

1) You will love the comfort seats if you have a bad back.
2) You avoid the "daddy's car" comments that will invariably occur on a daily basis.

I am more serious.

Just my $0.02.

 

Make sure you ask this question on the MB forum. I vote for the 5:
1) It is WAY more fun to drive.
2) Has the maintenance included (up to 50K)
3) Comfort seats option
4) Better resale value
5) Latest body style

 

I am surprised that nobody has mentioned that the MB S-Class essentially has no warranty left, which would make it a big no deal for me personally. The cost of maintaining a V8 German car out of warranty is simply too high. The 530i with comfort seats will be a better choice.

 

2007 BMW 530i def not an S-class

 

IF you want headaches get the S class. Have an S class now and would never buy another one. It is the biggest POS. Spends more time in the shop than on the road. Look around the net and you will see that it is a horrendous quality record. Esp if you are going to put 25,000 miles you better be will to spend that much to fix it yearly.