Well. OptiFine blends with the game better. You have shaders, connected textures, all sorts of features. Capes, client integration... I have to go with OptiFine. I really like how unobtrusive Sodium is, but until they implement ATLEAST zoom and shaders, OptiFine takes the crown for me. As a fellow modder I get the struggle, but still.
I'd honestly be willing to pay for the cape if they did one