NXGamer released his tech analysis of GTA 5 and made some pretty good comparisons.
https://m.youtube.com/watch?v=QhlLypEJq-c
So in summary from his video:
Tessellation on consoles is comparable to high on PC
Water on consoles is somewhere between high and very high on PC
Vegetation is very high on PS4 but high on XB1
Post FX is somewhere between high and very high. He couldn't tell much difference
Reflections in mirrors are ultra on PS4 but between high and very high elsewhere
Shadows are somewhere between high and very high on consoles with a soft look
Headlights from cars do not cast shadows on most objects on consoles
Also, the GTX 750 Ti runs a lot more like what I expected in this video. Rare minor dips below 30 but mostly hovering around 30-40FPS in car chases.