VFV is unhedged while VSP is hedged, and both are denominated in CAD.
Since VSP is hedged, it is equivalent to just the S&P 500 returns. The hedge is intended to protect investors from any potential appreciation of the CAD to the USD, since the ETF holds USD stocks. For example, if the S&P 500 returned 10% in a year, but the Canadian dollar appreciated relative to the USD, an investor holding an unhedged ETF would have a lower return than 10%, but the hedge works to offset this.
As VFV is unhedged, it is the S&P 500 returns + FX changes, and since the USD has appreciated relative to the CAD, when it is converted back to Canadian dollars, the ETF benefits from the FX changes relative to a hedged ETF.
Authors of this answer, directors, partners and/or officers of 5i Research and/or affiliated companies have a financial or other interest in VFV.