There is no problem with storing food in (stainless) steel containers. In fact, most gastronorm containers you see used by professional kitchen are made from stainless steel. This doesn't mean that they are somehow "the best" - they are as much suited for storing as many other types of container. If you have some special requirements, you have to find out what offers the best tradeoffs for your preference. If you don't, then it doesn't matter if you get stainless steel or something else that is suitable.