Which is better DEM or TIN?
What are the benefits/negatives of each?
It is all very dependent on your needs. You know that TIN is a vector-based representation whereas DEM is represented as a raster from grid of squares. Actually TIN is a type of DEM and derived from the raster DEM.
The TIN representation has information about altitude, slope and aspect and you can use them to extract the areas you require.
There is an information here about TIN and raster DEM.
Raster DEM and TIN examples:
Why You Might Want to Use a TIN
Data redundancy in areas of uniform terrain
Inability to adapt to areas of differing relief complexity
Exaggerated emphasis along the axis of the grid
Allows extra data in complex areas and less data in non-complex areas
The ability to use natural features as break-lines
Of course, you have to like triangles
I hope it helps you..