Without. In this case, separation feels like a misguided attempt to solve a different problem, which is lack of contrast between environments and characters. Obviously, there's only so much you can do with a relatively low number of available pixels and colors, and classic games often suffered from the same issue. But there are ways to highlight character sprites, make environments feel more in the background, etc. Try playing with colors a little more to achieve the effect of separation rather than actual physical separation.
