You should remember a couple of things about that. First, warm/hot water is better for some cleaning because the hot water can also provide a disinfecting action, and as stated above, some dirt releases better in warmer temperatures. Second, HE detergent is still full of fillers because pure detergents can be highly corrosive. Those fillers can build up on the drum and other surfaces of your machine, reducing efficiency. A good, hot wash helps dissolve that crud. But a general rule is always wash in the warmest water your fabrics allow. Cleaning cycles are generally bullshit, it depends primarily on how long it's being agitated in the water, how good your detergent works in said water, and how well the dirt is released in that combination of water and detergent. That being said, how much change can you do to a rotating drum? I would bet that "plus" just means it's in the water bath longer or it tries to agitate it more.