Recently, front-loading washing machines have increasingly been coming onto the American market. Many people don't realize that front-loaders were in fact the original kind of washing machine, and it's top-loaders that came later. People in other countries will wonder what I'm talking about, because front-loaders have always been the most popular washers all over the world... except in the United States.
With a top-loader, you can add an item once the cycle has begun. Of course, that means it won't be cleaned as fully as everything else in the load.
Some front loaders do not allow you to add an item once the cycle has begun. Indeed, some even lock the door so you can't accidentally open it and spill water. However, other models don't lock the door because the water line never reaches the level of the door, and you could add an item.
Front loading washers are very gentle with your clothes. The tumbling action of a front-loader is actually gentler than hand-washing your clothes. Basically, it gently lifts the clothes out of the water, and then drops them back in, over and over.
In contrast, most top loading washers have an agitator, which slaps and pushes the clothes around for the entire cycle. This is much harder on the clothes. Some agitators are harsher than others. Some are not quite but almost as gentle as a front-loading washer, while others (like, unfortunately, the one that comes with my apartment) are really clothes-mowers. Sadly, it takes a specialist to be able to tell the difference.
Many front-loading washers have a water heater. This heater is used to ensure that the temperature of the water in the wash is correct even if the hot water coming from the home isn't actually hot enough.
Front loading washers use substantially less water than top-loading washers with an equivalent load size. For the same size load, a top-loading washer uses about three times as much water as a front-loading washer. If you pay a water bill, the savings in cost of water can be substantial.
Front loading washers require less detergent than top loading washers. A front-loader generally uses half as much detergent for the same size load, or perhaps even less. Indeed, too much detergent is more of a concern with front-loaders, because if the detergent causes too much suds, the suds will inhibit proper cleaning. So, a front-loading washer creates an immediate cost savings in detergent.
Front loading washers use substantially less energy. Because they use less water to wash a load, that means that they use less *hot* water to wash a load, which means they use less energy to heat water.
Between lower energy usage, lower water usage, and lower detergent usage, a front-loading washing machine is substantially cheaper to own than a top-loading washing machine. Indeed, a front-loader is so much cheaper to own, the savings (versus cost of ownership of a top-loader) will pay for the average front-loader within a few years.
Some people complain about having to bend over to load and unload their front-loading washers. However, this should be no worse than their dryer, and most people have to bend over to get clothes out of the bottom of the inside of a top-loader anyway.
If you're interested in having a front-loading washer but are concerned about bending over, you can always have platform boxes made to place the washer and dryer on, to place them at a more comfortable height for you. A carpenter should be able to make such platform boxes fairly inexpensiely. You could even have drawers in them for additional storage.
Because of cost of ownership, quality of cleaning, and gentleness, I firmly recommend a front-loading washing machine.