I want to buy one for my wife.

Try a Lincoln MK X.

The MDX is probably the best of the bunch. It has plenty of power, handles and will haul plenty of people and cargo. It is new for 2007, with a more powerful motor and updated AWD system. It probably offers the best compromise between ride and handling. Reliability and resale have both been very good.

The Lexus RX350 just got more power, and was redesigned about 3 yrs ago. It is probably the most luxurious of the bunch. It is designed more to coddle it's occupants. Reliability and resale are both top notch. Overall it is probably not as roomy as the Acura.

The Infiniti is the sports car of the bunch. Sport models will ride harshly, but can hang with most any car in the corners. Interior space is compromised by the design, more form before function. It definately has distinctive looks, and has been around for about 4 yrs or so. Reliability and resale have both also been pretty good.

Overall I would pick the Acura. A fresh redesign and the best compromise between ride and handling. It just recently easily won a road test in Car and Driver (the Lexus and Infiniti were not in it). The Lexus is the best for a Realtor that wants to show off. The Infiniti is best for the guy that can't afford a Cayanne, but wants an SUV that will handle.

Any one of those are great vehicles. I wouldn't get the Infiniti because it costs so much more than the Acura and the Lexus, but if you're willing to spend that, why not? Anyway, the new MDX really looks good. I haven't driven one yet, but Acuras are great vehicles. The RX 350 is also very nice, but there's one problem with it: Lexus will most likely be redesigning it in a few years so you'll have an outdated car when it's still new. But if that doesn't bother you, then go ahead with that one! I personally would choose the RX 350 if it's for your wife. It's more of a personal vehicle and not as big. If you plan on carrying more passengers, then get the MDX.