hython $HFS/houdini/python2.7libs/opnode_sum.py > all_nodes.txt
If you run that from two different versions of hython, you can diff the results. For example, this compares 16.5.323 and 16.5.473:
And if you need to, you can add this flag to get all of the parameters and values, and diff those too:
hython $HFS/houdini/python2.7libs/opnode_sum.py -p > all_nodes_and_parms.txt
The version of hython being run is was really matters; you'll need to run the hython in each version of Houdini you wish to print out the list for.
Hope that helps!