We compare all-atom simulations of nanoscale water droplets of spherical and cylindrical morphologies on flat surfaces with tunable polarities. We find that for both morphologies, the contact angle depends, albeit differently, on the droplet size, which can be well described by the modified Young equation with an apparent line tension as a fitting parameter. In order to quantify the origin of the apparent line tension, we invoke a continuum-level description of the droplets for both morphologies. This enables us to decompose the apparent line tension into individual components that stem from a contact-angle dependent line tension and the Tolman correction to the surface tension.