The 2nd gen and 3rd gen share frames, the the latter being slightly revised for the rigidity and saftey reasons as well as to accommoate the el version. The front and rear suspension components were changed for cost savings (aluminum to steel) and interchangebility woth the f150. Also, interior parts were changed to use more f150(current ford products)parts. They also changed positioning of seats to add adjustability and space for passengers in all rows. Though not a full redesign, the 3rd gens changes were substantial enough to call it a separate gen. The 3rd gen has a nicer interior depending on trim and is a bit more refined in terms of noise isolation and ride quality, esp the latter years. The 2nd gen has a more raw feel to it. Its sportier, more harsh, louder, but has a way more connected feel, more tanklike, and has a more nimble feel. Also, the 2nd gen has more storage due to a larger console, column shift level, and larger storage pockets around the cabin. Passenger space wise, the third gen has redesigned seats and positioning that makes it far more comfortable, atleast in the first rows. As far as engine, the 3rd gens are faster trucks. The 5.4l 3v from my 05-06(2nd gen) and my 07-08(3rd gen) are problematic, so avoid those years. Some third gens get decent fe but its a wash. My 09 nav rwd avg 20 on the hwy. If you want comfort, a pre refreshed late model third gen expy/el(nav) with air suspension is one of the most comfy vehicles in autodome. 2nd gens with air sus are almost as comfy, but finding one without problems will be damn near impossible. For reliability and a daily driver thatll be rock solid, 04 expys are beloved by those who have em, check the 2nd gen threads and youll see what im tlkn about.