I have seen both of these ideas proposed on here as explanations for objects, including the Sun, appearing to sink below the horizon. Of the two, to Parsifal's credit, I find bendy light far, far, far more plausible, as it actually asserts an alternative behavior for light.
Perspective seems to assert that no matter how bright an object is (and the Sun is quite bright), it will eventually simply vanish out of sight at a certain distance, due to human sight limitation. This doesn't jive with the behavior of light as we understand it. As an object gets farther and farther away, its angular size will just get smaller and smaller until its structure can no longer be resolved and it will appear as a point source. As I've alluded to in other threads, light is simply oscillating electric and magnetic fields, which propagate in a certain direction at approximately 3 x 10^8 m/s. If a photon leaves a certain object, whether emitted or reflected by that object, that photon will continue to propagate until it interacts with matter or is reflected again. If light reflects off of a distant ship, that light will continue travel until it hits my eye and interacts with the photo-receptors on my retina. The photon isn't going to magically disappear because of perspective. If the Earth were indeed flat, the ship would just get smaller and smaller and smaller until it just becomes a tiny black dot. Its hull isn't going to start sinking below the horizon.
I propose this thread as a debate of merit between these two explanations.