How are ESRI WKT projections different from OGC WKT projections?

You've caught a lot of the differences. Esri never adopted the WKIDs for the map projection algorithms or parameter names so those are all different. We didn't agree with how carefully defined the parameter definitions are. Ours are more generalized.

We don't support TOWGS84 nor some of the newer keywords.

When we compare strings (names), we ignore the underscores, the GCS_ and D_, and case. That may not be true in other parsers. Our parser is strict on the names, but we've added some synonyms and now maintain lists of names from various vendors for comparisons.

The original coordinate system specification from OGC didn't get specific when it came to names of objects. There's a new OGC/ISO specification, "Geographic Information - Well Known Text for coordinate reference systems standard," making its way through the process towards standardization. It's much more specific about what the names should be (match EPSG registry!). It will be quite exciting implementing this standard in the future.

Disclosure: I work at Esri, am a member of the subcommittee that maintains the EPSG registry, and was a member of the CRS WKT 2.0 draft committee.

I don't have such a list, but going through the GDAL code will guide you:

https://svn.osgeo.org/gdal/trunk/autotest/osr/osr_esri.py

https://trac.osgeo.org/gdal/browser/trunk/gdal/ogr/ogr_srs_esri.cpp

https://trac.osgeo.org/gdal/browser/trunk/gdal/ogr/ogr_srs_esri_names.h

https://trac.osgeo.org/gdal/browser/trunk/gdal/ogr/ogrspatialreference.cpp