Each has advantages and disadvantages for both the tenant and the landlord.
Oral agreements are binding, but they are very difficult to prove.
The landlord can raise the rent, alter, or terminate the agreement at the end of any rental month, provided the proper notice is given. You and your landlord may agree on a longer notice period. Copies of a model notice of Intent to Vacate are available at Off-Campus Student Services. Always keep a copy of your written notice. Providing you don't breach your lease, the landlord is obligated to rent the unit to you for the length of time, under the conditions, and for the rent amount, outlined in the lease.