Best Efficiency or Highest Savings?
These may sound like the same thing when in fact they are quite different with respect to hot water heaters.
These days natural gas is much cheaper than electricity. So, if you have the option go with natural gas. Energy efficient water heaters that are gas have 3-6 times lower operating costs than electric heaters.
Should you buy a new energy efficient water heater?
This depends or your options for fuels and your budget. The info on this page should help you make your choice.