A wing, especially a quality built one, will generate more downforce than a flat plate splitter - hands down. A wing will have to be mounted in front of the nose, allowing for much more surface area. This is about the only location feasible because of the radiator support frame and hood location (unless you copy what @Mandan did with his 'mini' wings mounted to the sides of the hood, Canadians are so inventive).
But having a tilt in the splitter mount, to angle slightly upward, with good sized side plates that extend below and above the plate, and a Gurney flap will make a splitter much more effective too.
