Since your new washer is likely to last 10 to 15 years, you'll want to consider both your family's current and future size. Your laundry habits are also a consideration. There can also be seasonal factors, like sports and other outdoor activities, which might make a large capacity washer a welcome convenience. With more laundry rooms moving out of the basement and into living areas, quiet operation is becoming an important consideration. If you're looking for a quiet washer, be sure to check for insulation inside the cabinet.
Some models have sound-absorbing pads on all sides.
Quality engineering and design also play a big part in sound reduction. A strong frame and suspension can help reduce a washer's vibration from an unbalanced load. You'll want to ask your appliance dealer about the quality of the stabilizing springs on models you're considering, and be sure to check for thick rubber pads on the legs. They not only help reduce sound, they also protect your floors from scratches. Different washer models do vary in the amount of energy they use, and front-loading washers generally use less energy than top loaders.