I am using the schema compare feature of SQLDev often. It is very helpful to guarantee quality of delivery.
The goal is of course to find no differences between a source and target schema after an upgrade, but some differences can not be avoided. One is column order (for which we have an option to ignore), system generated objects and physical properties.
The following objects now cause a difference which should not be marked as a a difference (an option flag for it should be ok):
Index organized table overflow table. Should not compare names, only shape
Identity column generated sequences and default values. Should not compare the sequence names
Search index on JSON columns. Should ignore all system generated tables and indexes
Supplemental logging clauses. Often only used in production, not in reference (DEV) schema
NOVALIDATE of constraints. Sometimes used in production by DBAs to faster enable the constraints when it is known the existing data was ok before disabling.
Note: In the past I used SQL Developer Exchange for these requests, but it seems we cannot login to it anymore.