A flex lite isn't a treeless saddle. It still has a tree, but it isn't a solid tree and is designed to give. My friend has had hers for about 7 years and loves it. You do feel a lot of the horse's movement in them. They are comfortable to ride in though.
I personally like the one without tooling, but it depends on what kind of riding you are going to do. If you are going to do a lot roping or ponying then I would go with the solid tree.
If the tree on the tooled saddle is wood wrapped in bull hide or rawhide, it will last forever as long as you take care of it. If it's a newer saddle it probably has a ralide tree which is fiberglass over wood. That's what mine is and it only had a 5 year warranty on the tree, but I've had it for 8 years now no issues.