In my opinion any game type with pvp should have pets disabled because it's not just slimes and magma cubes people are abusing taking away just this 1 pet won't help because other pets can do the exact same thing
I think that only slimes & magma cubes should be disabled on the PvP gamemodes. The other pets shouldn't be though, as they are smaller (eg. wolves, chickens, pigs, etc). Thanks for your opinion though