Personally I'm a big fan of sonic ice myself. The now popular "nugget" (or pearl or cubelet) ice has that easy-to-chew texture that keeps me coming back for more. This type of ice actually absorbs the flavor of the beverage it's sitting in so the customer can "crunch" on that flavor long after the drink is gone.
Larger cubes are the most common in restaurants. They take longer to melt and a large surface area to take up more space in the consumer's cups, increasing profitability on those free-refill beverages. All of the previous posters on this subject are correct, shaved or flake ice melts way too quickly and should never be used in a drink. This type of ice is better for snow cones and displaying seafood.
It really just all depends on what you plan on using the ice for. But in my personal opinion the "nugget" is quickly becoming the most versatile and popular in the industry.