They are both crossover one shots of popular Jump series and are done by famous Jump artists. Jump Super Stars is more of promotional manga for a game so lacks some of the heart that Cross Epoch has which comes across to me as a passion project of Oda's.
These are both one shots by famed Shonen Jump mangaka. Cross Epoch is collab between two of manga's biggest names Akira Toriyama & Eiichiro Oda creators of Dragon Ball, Dr. Slump & One Piece. Burn The Witch is by another household manga name, Tite Kubo creator of Bleach & Zombie Powder. They are both short & easy to digest with great art. Fans of Shonen, Jump or any of the artists famous work are likely to enjoy both of these one shots.
Like the Toriyama collection, Cross Epoch is a one shot with involvement by the legendary mangaka Akira Toriyama. Unlike his collection which is all solo work, it is a collaboration one shot with One Piece creator Oda. If you enjoy this manga and Tori's Style/work in general you should get some enjoyment from this one shot.
These are both hidden gems for the Dragon Ball fan seeking new content. One is a collab one shot with famed One Piece creator Oda, the other a story of a hardcore Fan reincarnated in the DB world.....as Yamcha! They're both short, easy to digest and target the same demographic. Fans of Dragon Ball, One Piece, Tori or Oda will find enjoyment in both.