888 is super smooth and an all around great player the shape feels great in hand and spins are everlasting. Its small enough to be a pocket yoyo yet wide enough so it is very easy to land on the string. I have never tried a superstar so I dont know much about them though
The 888 is small, wide, and nice and speedy.
However, the Superstar is bigger, has a slight H-Shape, and is a smooth player also.
Still, IMO, the 888 is better, due to its size, however, the superstar has longer spin, IMO. They ae both very smooth players, but I think the SS is better if your style is slower.