The Japanese were tougher...the Pacific campaign was way harder than the European -- at least for Americans. Read some of the projections of what would have happened if we'd needed to invade Japan. Potentially a million Americans and 10 million Japanese. That's one reason we used the a-bomb.
Germany had better weaponry. They were much further advanced. Hitler made key mistakes. Dunkirk was a mistake. Invading the Soviet Union and having a two-front war was a mistake. The worst by far was the Holocaust. If Hitler had instead embraced the German Jews and used them in the war effort, Germany likely wins and takes all of Europe, including the UK.