The real difference between the two products is that oil is much slower drying and so is more suited to blending techniques - so as one shade move into another, the join is almost imperceptible (so it looks like the dark brown horse is oil) - while acrylic can't do this as well, but is very good for layering contrasting shades and highlighting quickly (I assume the horse on the left has had that technique) - so each require their own technique and get their own look - though in this example, both look rather fine and it would be hard to choose.