Advantage:
1. Easier to control with an engine failure
2. Lower VMC hence a construction of a small Rudder area (saves weight)
3. Aerodynamically clean wing
4. Less cabin Noise
5. Uncontained failure will not damage wing area i.e leading edge slats etc ..
6. Aircraft looks better
Disadvantage:
1. Difficult access for engines during maintenance
2. The missing engine weight underneath the wing requires more strengthened wing structure to avoid high bending forces
3. Longer tubing required for hydraulic and fuel lines which adds extra weight
4. Possible damage from landing gear deflection.
5. T tail design required resulting in super stall characteristics
6. Airflow interference between fuselage and engine Inlet
7. Due to missing engine pylons more modification needs to be done on the wing to avoid Spanwise flow and wingtip stall.