The difference between Kerr and Ball Jars is in the appearance and the mold used to make the jars.
The Kerr and Ball Jars are made in different molds so the appearance is just a bit a different but the glass jars are the same as they are made from the same glass.
Both Ball and Kerr brands are now owned and manufactured by the parent company Jarden.
The glass is made in the same batch, the only differences are the molds - whether they say "Ball" or "Kerr" is only cosmetic.
So other than the cosmetics of the canning jars they are essentially the same type of jars.
Both Kerr and Ball Jars are good quality canning jars and it does not matter which type of canning jars you use.
Also all of the jar companies have both regular size and wide mouth.
Kerr & Ball jar lids are interchangeable.