535i vs. 550i

[FSETH]

I never really looked at the numbers for these two cars back-to-back until today and I was surprised. First of all here are the specs;

535i $49,400 base, 300 hp/300 lb.ft., 3660 lbs. 0-60 5.6 sec 17/26 mpg
550i $58,500 base, 360 hp/360 lb.ft., 3946 lbs. 0-60 5.4 sec 15/22 mpg

So what do you get with the 550i over the 535i? It costs nearly $10k more, it gets worse gas mileage, it is 300 pounds heavier and it is only 2/10's of a second faster to 60 mph??? I don't see how BMW is selling any of these. If you add in the Dinan software for the 535i, you are still nearly $8k less and now you are smoking 550's. What is the point of the 550i right now? I would assume that the 4.4 twin-turbo will be replacing the n/a V8 ASAP.

By the way, the above figures were for the manual trans. models.