My experience is.. I saved up from previous season 1300 skill points...didnt assigned them.. league was easy obviously ... tomorrow I will clinch title... but CUP - I have never won ... and I am playing finals as when I assigned my skill points I was more than equal to the guys who were 1-2 cup level higher than me.... so YES - CUP is definitely easier ... league is easy too... and CL you dont play if you tank.... hope it helps