In general: neither. The advice is to have the full source tree in /opt/ledgersmb/<version>.
Installing the LedgerSMB modules in the standard Perl search path works, but interferes with running different versions side-by-side.
To undo installation in /usr/local:
- remove /usr/local/share/perl/5.XX.X/LedgerSMB/
- delete /usr/local/share/perl/5.XX.X/LedgerSMB.pm; and
- find and remove the .pl files that come in LedgerSMB's project root directory and bin/ and LedgerSMB/Scripts/ directories.