I don't think there's anything especially distinguishing between them.
Animas vibe can integrated with the dexcom G4 if that's something you would be interested in funding.
Medtronic 640 can integrate with an enlite CGM and that would give the pump a predictive low suspend feature.
Best idea would be to get hold of the pumps - see if the hospital has demo pumps where you can actually handle them, press the buttons, see the screen. That should help you figure out which on suits you best. If you can't do that, have a search on YouTube for each of the pumps and you should be able to find people using them, siting the cannulas and wearing pumps on belts or on their waistbands or slipped into their pocket, which might give you more of an idea of what you would prefer in a pump.