Bonanza Bros.: I never played these games, but going solely from the screenshots, both versions seem nice and on par with each other. Sure, I could point out some things (see the last pic in the series, with the coal mine car) and give the edge to the pce, but...
There are some aesthetic decisions that seem to favor the pce: the gradient and perspective on the tiled floor, for example. Or the backgrounds.
Bonanza Bros. was a PCE CD, correct? Did it offer a nice soundtrack compared to the cart?