Yu Yu Hakusho on average only has as much violence as the standard battle shounen, but there are a few instances that cross the line. Those instances involve multiple decapitations, amputations, mass death, cannibalism, torture, implied rape, disintegration, brainwashing, and a few blood baths. Those events are not overly gory and happen rarely so the series can be safely watched by older teens.
Yu Yu Hakusho is Bleach, but shorter and with less filler. Both series feature a student, juvenile delinquent who meets a female shinigami and ends up working with that shinigami (who decides to also go to his school often) to help spirits travel to to afterlife. The series then changes to a battle shounen and the protagonist teams up with his friends to fight monsters.
Showing any more similarity crosses into spoiler territory, but the main difference between the series is that YYH focuses more on developing the characters.
JaserHyakuya asksDoes Guren's bond with Noya make him stronger than The Absolute Sword, Zekken? "It pains me to see someone so pitifully weak," Guren said with a laugh, drawing his sword. Shadows escaped from the sheathe.
Yuuik just smiled. This guy had fake power from a demon. She had... Mother's Rosario!