For the cartographic boundary files, the data from the Census site have been generalized from the original TIGER/Line data, whereas the files downloaded from Esri still maintain the original detail.
Files on the Census site can also be downloaded by state and/or for the entire nation, depending on the layer. So if the generalization is acceptable, the Census site is the best source for large amounts of data. The Census Bureau (www.census.gov) also offers the files as shapefiles, Arc Info export files (.e00), and Arc Info ungenerate (ASCII) files.
For other geographic files (water, etc.) and for the attribute tables (PL-94 and SF1) that can be downloaded from Esri, the Census site does not offer downloadable files that are ready to use with Esri software. These geographic files are available only in TIGER format, so they have to be converted into a coverage or shapefile. The attribute files can only be downloaded from the Census site as huge text files that have to be reformatted, and that contain hundreds of attributes per file. Esri extracted from these huge files only the attributes that were wanted and assigned meaningful names to the fields in the tables.