Black Widow would win. Yes, they both have years of experience, but what really swayed my opinion was the fact that Ollie couldn't beat a man who only trained one year in Nanda Parbat. If a man with only a year of non-stop combat training can beat a man who spent 5 non-stop years surviving on an island, than Black Widow has this. Not only is she a combat expert, but I'm pretty sure she has spent more than 5 years doing survival training. Ollie is outclassed in this.