Advantages

Guaranteed Retirement Income: Employees are promised a specific monthly benefit upon retirement, providing financial security and predictability. The amount is usually calculated based on factors like years of service and salary.

Employer Bears Investment Risk: The employer is responsible for funding the plan and managing the investments. Employees receive their promised benefits regardless of the plan’s investment performance.

No Investment Decisions Required: Employees are not required to make investment decisions or worry about market fluctuations, which can simplify retirement planning.

Predictable Payouts: The benefit is often based on a formula that includes years of service and salary, making it easier for employees to estimate their retirement income.

Potential for Early Retirement Benefits: Some defined benefit plans offer early retirement options with reduced benefits, which can be appealing to employees who want to retire before the typical retirement age.

Spousal Benefits: Many DB plans include options for spousal benefits, providing financial security to a surviving spouse in the event of the employee's death.

Disadvantages

Lack of Portability:
Defined benefit plans are generally not portable. If an employee leaves a company before becoming fully vested, they may lose some or all of their pension benefits. Even if vested, the benefits are often frozen at the level they were when the employee left the company.

Limited Control:
Employees have no control over the investment of the plan’s assets, and the benefit amount is fixed by the plan’s formula, not by individual contributions or investment performance.

Employer Funding Risk:
If the employer faces financial difficulties, the pension plan may be underfunded. In extreme cases, if the company goes bankrupt, the pension benefits might be reduced, although some protections exist under programs like the Pension Benefit Guaranty Corporation (PBGC) in the U.S.

Inflexibility: DB plans usually offer fewer options for accessing funds before retirement compared to defined contribution plans. Early withdrawals or loans against the plan are typically not allowed.

Costly for Employers:
Defined benefit plans can be expensive for employers to maintain, particularly if they must make up for investment shortfalls or changes in actuarial assumptions. This has led many employers to freeze or close DB plans in favor of defined contribution plans.

Inflation Risk:
Unless the plan includes cost-of-living adjustments (COLAs), the fixed benefit amount may lose purchasing power over time due to inflation, which could erode the value of retirement income.