from my experience at firestone
infiniti QX4-quality, usually odd tire sizes sometimes hard to find, when stuff breaks its very very pricey
Ford Expedition Eddie Bauer- overall decent probabaly on par with the tahoe for gas mileage. some front end issues but thats the nature of the beast with big vehicles
Toyota 4 Runner-bearings, bad axles, hell a brake job can cost you and arm and a leg.. I'd stay away from the toyota. If you want a luxo suv get the infiniti.
Chevy Tahoe-fuel pumps, injectors, bad front end parts, rotors that crack from severe heat easily.
depending on if you're rich or not get the infiniti first, if you're not go with the expedition. then the ttahoe then the toyota. Best quality suv out there right now is the trailblazers and envoys. I'd look into them seriously bnefore buying a different suv..