I think having a regular spare beats run-flat tires any day. I've only had one flat in the last 35 years, and the mini-spare worked just fine. I'm sure it would for the ML as well.
I did take the spare out just to look at it and measure it - weighs about 40 lbs or so, is a LOT more skinny than the tires on the car, comical actually, but it is properly load rated and does measure the correct diameter so the 4-matic won't go nuts. I've driven an ML with run flats - and hands down, I'd not have run flat tires because I consider the ride on run-flat tires to be plain awful. I know it's a compromise - I'd rather carry the 40 lbs in the trunk.
I guess if I had to do it over, I'd still have the CDI for long trips simply because of the fuel mileage, and all around practicality, and have an AMG CL instead of the SUV. The AMG engine sounds are just sooooo sexy and as I've already said - just touch the throttle and it wants to go.
AMG for sure like - two SUVs, not so much sense - you might be just the shove for me to reorganize the garage. If you want, I'll sell you my '09 for mid $50's -16,500 miles give or take. It has two somewhat unique features - it was ordered with the euro alcantara sport seats instead of leather (no charge option though blue-book wants $750 less for car built that way), and it has a painted bumper brace (again euro) instead of a black bar. And I put Brabus wheels on it at a cost of $5K. Otherwise a full boat AMG with everything checked out by dealer just before warranty expired - including replacing the two front airmatic /ADS struts (about $8000 worth !!!) on basis of tech bulletin - nice dealer mine.
Send me a PM if interested. I drive the AMG about 200 miles per month on weekends mostly - and as I already stated above - I'd turn around and get an AMG CL, keeping the CDI SUV. The CDI gets 1500 miles per month by comparison - parked at the airport during the week where I would not park the AMG.
So there - you know exactly how I feel. The AMG around town with it's lightning reflexes, the CDI for trips with it's mileage. If I could only have one ... well I'm glad I don't have to choose. It would be like having to marry one girlfriend and give the other one up. Sigh !
Aw heck - now I'm vacillating again = the ML-AMG is so much easier to get in and out of than a CL.