Both are very good. JJK it's a well written battle shonen, beside I don't see CSM in the same gender.
Chainsaw's action scenes are basically a visual appeal to entertain the reader, they're amazing but has a simple narrative. On the other hand Jujutsu brings a more complex power system and a lot of text inside its fights (HxH vibes).
For the art, panneling and imagery i rather CSM. Fujimoto's art is great and versatile. We also have excellent references to trash movies and art pieces.
Storyline i give the edge to JJK for presenting a more linear plot, which is perhaps better for the vast majority of readers. However I must say that sometimes I prefer the unpredictability of CSM.
Both series had very interesting characters. JKK has a very charismatic and cool cast, but i rather CSM in this point. Although his characters seem shallow and silly at first glance, after thinking a little it is possible to notice ideas and concepts behind them (heritage from Fire Punch).
I must say that I like CSM a lot more than JKK, not because of the lack of quality in the last one, but because I'm not so interested in WSJ battle shonens anymore (except for series that I've been following for a while).
Also, CSM part 2 will be a slice of life in school, just wait
Finally, I hope Gege Akutami's health improves soon so he can bring more chapters to his fans;