I was in the same boat exactly 2 years ago. Here's how I made my decision:
1) interior usable space - expedition wins over Tahoe / Yukon hands down. The fold flat 3rd row is a huge step up from the GM standard length SUVs this regard (theirs flip forward, and are able to be removed. power fold flat is HUGE). When comparing the Expedition EL vs. the Suburban / Yukon XL, the Expedition wins again. It's a bigger vehicle, and the engineers made sure to make the extra exterior space show up on the interior too. The Suburban / Yukon XL gives more 3rd row foot and leg room vs. the Tahoe / Yukon, but the standard-length Expedition gives still more. The only thing to look at is whether you will ever have more than 4 people in the car, if so, this is a big deal. If not, don't worry about it. I went with a standard length Expedition Limited, and will plan to go to an EL or Navigator L if/when we have child #3.
2) exterior styling - it was honestly a toss-up between the Denali / Escalade and Expedition Limited. All of them look good. Some days wish I had the growl that the Denali exhaust has from the factory, but that's only a muffler swap away.
3) reliability - these are all big trucks, can handle serious work and if maintained well will last a LONG time. My '08 Expedition with 50k miles is the stiffest, most sturdy vehicle I've ever owned. The doors on it close more solidly than my '11 Lincoln MKX and my '08 BMW 5 series. It rolls down the highway better than any car I've ever owned, those other two included. The paint bubbling is a PITA, but if you get a new one or one under its 3/36 warranty, any paint bubbling issues will be taken care of under warranty. Just make sure to do a thorough check before you roll over that 36k mile mark.
4) fuel economy - none are great, but honestly they are all better than they have any right to be. Big, heavy, tall bricks rolling down the road, powered by 300+ hp V8s don't get good fuel economy. The Expedition is much better than my Wife's prior car, the underpowered Hummer H3.
5) price- the Expedition is a good deal, when compared to the GM versions. You can get a fully loaded up Limited or King Ranch for many 1,000s less than the Denali / Tahoe LTZ / Escalade.
I wear 12's and don't have a prob sitting in 3rd row...5'11 and I'm always in 3rd row tuning my system
I'm 6'1, 220 lbs and wear size 13. I have sat in the 3rd row for a couple quick trips around town, and it was quite comfortable.