Spend more time with the models!
OP, depending on how important the car is to you, you might very well benefit from an extended test drive of the cars in question. I wouldn't rely much on the sales rep for questions beyond the basics. Unless you meet one who is a died in the wool enthusiast, they'll basically tell you something (or avoid the right answer) just to get the car sold. Find out all you need technically from enthusiast or forums like this. After you found the car you want, then spend the sweat with the sales rep when it comes to ordering/trading/selling you a car.
If you're area has limited inventory, it might well pay you to do a day trip some weekend to a city that has a lot of cars to see/drive/compare. Where I live (LA) there are over a dozen BMW dealers with 100's of F10's and even a few M5's on the lot (not too many 550xi's). I'm not suggesting you have to come to LA but I would think a city within a couple hours drive away, or even a cheap commuter flight to some big city, would serve good purpose if you really want to compare models. You might even check BMWNA website for model search and it'll point the way to where certain cars are and the related equipment.
And yes....the 550i will cost more. Everything being equal option wise, there will be about a $5000 difference.
And the gas milage will be better with the 535i but simple math might bear on this a little light on this subject. Assume a 535i ad 550i both drive 10K/year. Assume the 535i averaged 25 mpg and the 550i 20 mpg. Then the 535i uses 400 gallons/year and the 550i uses 500 gal/yr. At $4.00 gal, that's $1600 vs $2000 annual fuel cost. This is a rough guide, not scientific or proven, but a reasonable comparison....your actual milage will vary.
Other posters don't kill me on this gas thing (I do about 80% interstate and see 27MPG regularly) but I'm sure if it were reversed for city driving, I'd be in the teen (lol).
So, a 535i or 550i? There's no wrong choice...only choices depending on you!
Last edited by HDEddie1; 01-15-2013 at 02:09 PM.