I can answer the first question...
A suspension lift replaces parts of your suspension, so it lowers the axles, and raises the frame... this, plus bigger tires, is what gives you a lot of ground clearance so you can go over boulders and junk...
A body lift replaces your body mounts... Your body is raised off the frame, and your bigger tires are the only thing that gives you more ground clearance...
A body lift is pretty much good for looks and to get bigger tires... It's also a cheap lift kit if you're not a hardcore wheeler, but like the look of a lifted truck... The only problem with body lifts, as far as looks, is on some vehicles you can see the frame under the body after the lift... That doesn't look so good in my opinion, but whatever makes ya happy I guess...
A suspension lift is probably your best bet... They cost a LOT more, but it's worth it, because getting a 3 inch suspension lift vs. a 3 inch body lift not only LOOKS better, but you also have 3 inches of extra ground clearance (plus, again, whatever you gain from bigger tires, probably around 4-5 inches total lift) for going over boulders, trees, sleeping bears, and such...
About wheel travel... I have no clue, never heard of it...