There is no way in hell an S62 is nearly 100 lbs lighter than an s65. They are both aluminum V8s with roughly the same size block. Just putting that out there.
One could build a bored/stroked 7000 RPM S65 with 400 hp, but that would be seen as a big waste of money and a step backward by most. Similarly one could build a destroked 8400 RPM S62 with 414 hp but that would be seen as a waste of resources as well.
For racing applications, either engine is capable of 600hp+ once you equalize displacement and RPM. The S62 may have a higher deck (not sure) which would mean more displacement potential in theory. Both have an 98mm bore center like all BMW V8s. For a race series that does not allow altering the short block from stock, the S62 obviously has the advantage.