Curve Fit
The curve fit chart gives you a quick visual assessment of the fit of each model to the obversed values. From this plot, it appears that the Quadratic model better follows the shape of the data. In particular, the linear model seems to overestimate sales for cases with small or large values of Advertising spending and underestimate sales for cases with medium values of Advertising spending. As a further visual check, you should look at plots of the residuals versus predicted values for each model.