They have a much better design than the blue shell.

In Mario, the guy in 8th place sends a bomb into the ether, and sends the guy in 1st place to 5th…while the guy in 8th stays there.

In Sonic, the guy in 8th sends a swarm of hornets, essentially a minefield. The guy in first CAN evade them skillfully, but has the most to deal with. As more people hit some, others will have fewer. The whole crowd gets slowed just a bit (and the person who threw it is unaffected when they reach them)