The mercedes and the range rovers are really much smaller, that is our issue. Also, when I drove the mercedes, I didn't think it drove as nice as the Q. Our only issue with the Q, other than the price, is the size. (need big). We've pretty much ruled out the sequoia after today, so now down to armada and q. Still struggling....
I just took a look at the specs on the Armada, QX, and Mercedes GL. They are all within two inches of each other, except overall length (the Mercedes is about six inches shorter, although the wheelbase is the same), 2nd row leg room (the Armada and QX rule here, about three inches more than the Merc), and 3rd row leg (the Merc is three inches more than the Armada, six inches more than the QX). Couldn't see much difference between the QX and the Armada in key specs, except 3rd row leg room. Towing, the Armada is highest, Merc lowest (but still 7500 pounds, which ain't bad). The Merc gets pricey in a hurry, it isn't any problem at all to get up into the mid 70's. The QX is mid 60's nicely loaded. The Armada is much lower, mid 40's after rebates and discounts, which are very plentiful. If you can find it, a fully loaded 2012 Platinum 4WD can be had for the low 40's. But, in my mind, the QX and Merc are a notch above the Armada in drive quality, refinement, and luxury. That's what the extra 20 to 30K gets you!!
The wife and I have been kicking the idea around of replacing our 2006 Armada, which has 82,000 miles on it right now. We still like it, and would consider a replacement Armada, but really like the new QX. Haven't driven or looked at the new Merc yet. Sequoia isn't an option, just don't like them. Waiting for the next generation Tahoe / Denali / Suburban to come out from GM. GM is on a roll right now, so hopefully they'll continue with these vehicles.