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
I hope it helps you..