For starters, today's models have child lockouts with keypad releases. Other improvements include automatic defrosting and a range of programmed power and time settings for the most popular microwave foods, such as pizzas, popcorn, and packaged dinners. Some models even organize foods by ethnic category, such as Chinese and Italian, and cook accordingly. While such features may be handy, the real differences are in power, capacity, cooking sensors, and convection-heat options. Power is measured in watts, starting at 600 and ending near 1000.
More power means shorter cooking times.
You probably won't want less than 700 watts because the recommended cooking times for packaged foods assume at least that amount. Power is usually coupled with size. Cabinet sizes start at around 0.5 cubic feet and end near 1.3 cubic feet. Many models have built-in sensors that prevent food from overcooking by monitoring moisture levels. Some top-end models add convection heat so foods can be browned without moving to a conventional oven before serving.