Just because an object has a Need fulfillment rating of 5 and another has 6, that does not necessarily mean that the difference between the two will be equal to the difference between a 6 and a 7. For example, the difference between the cheap refrigerator (Hunger 6) and the expensive refrigerator (Hunger 8) is +2. But that is only about half as effective as having a food processor. For $220, you can get twice as much out of making a meal, than if you spend $2500 on a new refrigerator! You'll have to experiment with all of the different objects to find out which ones really are the best. The ratings are a good general guide, but after using all of the objects, it will be easier to make a better choice for your money.
For more Tips & Tricks for playing The Sims, including Time Management, building Skills, and getting more money, click here.