1.Leading ledger is a parent ledger which means non leading ledger derives all value from the leading ledger like parallel currencies, posting and all.
2. All documents posted in leading ledgers automatically flowed to the non leading ledger but not the vice versa.
3. When you post document for non leading ledger you will have to mention Ledger but not in the case when you post for leading ledger.
4. Leading ledger is the Primary ledger whereas non leading ledger is secondary one.