New slime or evolution?

Hello! I am collecting a castle shards and I thought, that I will spend it on a new slime (Woodman Slime, SS), but now I am thinking about evolution of amber (140 lvl, rare favourite toy 13 lvl) and then upgrade him. At the moment, my best slime is Serpine with 200 lvl and epic hero sword 31 lvl. What is better decision?