Argument: Very few sites globally are appropriate for tidal energy
"PROS AND CONS OF TIDAL ENERGY USE". Energy Consumers Edge - The key to reliable, economic power from tidal energy involves properly engineered, economical turbine generators placed at well researched sites with high tidal flow rates.
Because of intermittency and variable flow problems of tidal energy, it is a very limited resource. The DOE Tidal Energy link, above, states that there are only about 40 really good sites on Earth with high enough flows to be considered economically practical.