I was helping a customer select a new garbage disposal and was once again impressed by the range of products available from InSinkErator. They have a large line of products for almost every price range. Like with anything the quality will vary with the price, but there are lots of good options in the mid range to choose from.
Overall, the horsepower needs to match the user's needs. This picture posted on the product display shelf of the InSinkErator line sums it all up. How much food scraps do you expect to dispose of? Make sure the horse power of the unit will meet your needs when you buy a new garbage disposal.