Since almost all my jackets, jeans and trousers are blue, I would never buy a blue bag like Cobalt. It would just be too much blue .I'll be a fly in the ointment ~ Messenger Greenwich ~ Damier Cobalt. It's sleek and suits casual and formal situations. But out of your three choices I like PDV GM the best.
pdv more professional looking than kitan
keepall is more a travel bag to me , unless you go to the gym everyday then its different ...