Good fight, but DS would eventually win. The only reason Arrow won against DS was because he lost the Mirakuru and was disoriented after that. With the mirakuru, those guys were tanking gunshots at point blank range. WS doesn't have that kind of durability. It was even mentioned that their skin had the density of concrete or something liek that. Plus Slade's mirakuru children had strength feats better than Cap and WS.
As for fighting skill, Slade might not have shown much in the last few episodes of Arrow, but he showed pretty good skill during the first season before mirakuru.