Prior to 1.5, the Subversion team mergedid not leave much information about which branches were reintegrated into the trunk, so svnmerge.py was written to compensate for this lack of traceability.
Starting with version 1.5, meta-information is generated by svn at each merge, a property svn:mergeinfothat is transparently added to the target paths. You can appreciate this, for example, if you use TortoiseSVN, which can show you a graph.
This is not entirely true, but as many would correctly say .
So, you should understand what you need, if the standard is svn mergenot enough for you, look at the type scripts svnmerge, but in this case make sure that everyone uses the same tool.
In my experience, the standard version is more than enough in most cases.