Single lease: joint liability as a safety net
With a single lease, all co-tenants sign the same contract and are jointly liable for the total rent. If one of them doesn’t pay, the others must compensate. This is the most secure option for the landlord.
The difficulty arises when a co-tenant leaves: an addendum to the lease is needed to formalise the replacement.
Separate leases: more flexibility
Each co-tenant has their own lease for their room and a share of the common areas. The landlord manages more contracts, but each tenant is only responsible for their share.
This formula is preferred by owners of student rooms and large shared houses.