back to the original question....both are good trucks.
The excursion is obviously bigger all around, it has a solid front axle (D50 I believe), better motor options (diesel for the win!), and will be better for towing because of the increased weight....plus more room for the family.
The expedition isn't a bad vehicle though...plenty of room for 4 comfortably, but can hold 7 if you have the third row seat, but not much room for adults in the very back.
We have a 98 eddie bauer up at our cabin for a farm truck/weekend vehicle. My parents bought it new in 97 and have put around 300k on it. It is on its third motor though, first one dropped a valve at 105k miles, and they replaced that with a garbage re-man motor that kept spitting head gaskets and leaking oil...so that was ripped out for a 5.4 that came out of a wrecked 99 expedition which had 13k miles on it...great truck since then. My dad uses it to tow his quads, and pull all kinds of stuff around the property.
If you are leaning towards an expedition, go for a 99 or newer. The 97-98's weren't bad, but the 99+ got the PI 5.4, which bumped the HP up to 260 from 235. Or if you get an 03 or newer, it will have the 300hp 5.4.
Now as far as the excursions go...the 05 was the best model. It has the coil spring front end instead of the leafs, and it will have a muuccchhhh better turning radius. Plus it has the updated grill/bumper/lights, so it looks a lot better. But there is really nothing wrong with the older models.
If you decide to go diesel (which I would highly recommend if you really plan on towing with it) I would shy away from an 03 or 04 6.0, because they had a lot of problems. The later build 04's and 05's were pretty solid, and have very few problems if any....but they wont come cheap unless they have a ton of miles on them. The older models with the 7.3 are tried and true, and will run for a long time. You can get a tuner, exhaust, and intake and pull 20+mpg with it...which you will never get with a 5.4 or 6.8.