among the options you've suggested, I'd recommend that you go for 6681. Good phone, 1.3mp cam. Go for 6680 only if you need the second camera for video call, which is highly unlikely in India.
secondly, Motorola v3 and v3i have poor build quality and associated software problems. The rotating hinge get loose after sometime and the main software problem is missing entries of phonebook. Every other day some entries from the phonebook keep on 'vanishing'. Yes, you heard it right, 'vanish'. Secondly, Motorola phones need to be handled with more care, they're more prone to physical shocks and damage the way we handle phones and repairs are also very costly. How do I know all this? I own this phone.