India have won games convincingly both bowling and batting first. They don't need to test anything.If india win toss, they should consider putting SA in to test their bowling against SA in preparation for the knockout phases.
SA on the other hand has only won games while batting first, lost one while chasing against ned and almost lost to pak while chasing. They should consider bowling first to test their chasing.
India should just bat first if they win the toss.