Hello Jonathan, the entire TIN dataset is always evaluated at once, whereas the terrain dataset has a tiling mechanism that's used in analysis operations. The default behavior utilizes a dynamic tile size but an environment setting is available to force the terrain to use its own predefined tile size. This tiling process may potentially account for some discrepancy. Using the environment setting to force the terrain tile size to be used would ensure the same results. If you see it doing otherwise, please share your results and let's see if we can figure out what's going on/