An example of wholesome thread :)
Of course having everything in 3d is my preferred method, and it was the obvious choice for me to do (and the easiest I believe), but I decided to freshen up a bit and take the challenge.
Decals are not perfect, as they just project texture/light, they are not blocked by geometry. Having everything in 3d (you just need to have enough, not everything perfectly) and as real-life simulated as possible, is the best; think about changing light direction, animating the sun and opening of blinds, maybe some wind, or a blurred tree/leaves shadow from outside - all of this will be better with lights and 3d blinds.
Remember that it is CG, it just needs to look good/correct, and you just figure out what is the necessary part.