Yes, the advantage is that you get a terrain that loads fast and you can change values like deatails etc just like a terrain file.
The disadvantage is, you get a terrain that is DYNAMIC, its set to take actions and therefore, is already a resource hog and you will get prolems with other models walking on it, they appear black!
Importing the file thru WED however will make it static just like a block BUT then you get probs with multi skins and so on.
The best method that returns all expectations is to use a proper terrain file BUT not as a single item if you dont use 'chunking', rather as multiples of 100 polies each segment or similar so that clipping works for the terrain (or the model file) from any distance, other wise, use 'chunking'.
If dynamic is reset on your model terrain you wont need to add poly collision to the model, its done already due to being static.
Personally, I dont know the real difference if you are working thru small levels but a big game will need attention to using the right resource for the game.
