Cultus and WagonR are not fully automatic, both use electronic gearshift, while picante is true 4 speed automatic.
Cultus and WagonR have more cabin space, better resale and Cultus really outshine any competition in fuel economy.
Picanto has best build quality and finishing among these three and paint quality is way better, Downside is expensive maintenance, low fuel economy and resale.
Rest I would suggest, take test drive of all three and then decide.