Those preset formations are quite meaningless if you are the attacer (wich is the only case in wich ull use them) you are not stressed to have your formation ready at the start of the battle but cacn instead position your troops after the start of the battle to strike the defender correctly. Still I usualy select Scorpton beacause its the way I usualy play, grunts in the middle and flank with cavalry + having some supporting cavalry at the end to send where its needed)