2nd generation Expeditions 2003-2006 got a lot of improvements including independant suspension, 1st gen had a regular solid axle.
3rg generation 2007+ got more improvements including the 6 speed transmission, and higher payload. I would definately stick with the 3rd gen
The 6 speeds make the axle ratio a moot point. 4.1 is not available for Ford or GM 6spd, nor required with the due to the wide ratio spread.
While the Sequoia is nice, it would be at the bottom of my list due to payload. Most Sequoias have 1200-1300lbs, several hundred less than GM or Ford. OP has a growing family and wants to pull a trailer, possibly moving up in size. The Sequoia will hit that payload limit quickly.
My family of 5 plus Aunt, car seats, strollers, misc bags weighs 825lbs. My Expy EL has a payload limit of 1672lbs, so 1672-825 = 847 available for hitch weight, plenty for my trailer, and room for the kids to grow. A payload of 1300lbs would leave me with 475lbs, not even enough for my current trailer. Low payloads are the achilies heal of 1/2 ton.
