Both outfits are divine. Regardless of which you prefer to wear, think of the occassion that you are wearing them to. If this event is morning/afternoon go for the python combo. But if this is evening, you should consider the black/nude combo with great jewelry.
Yes, let's also not forget the don't wear white to a wedding rule, but I've never been to a cotillion. In general the black combo makes you look curvier and thinner. Tres chic!
If you decide to wear the python anyway, how are you getting to the event? If you are driving and going to valet the car, wear crappy old back up shoes and change them right before you pull up to the valet. Regardless of how durable the python is, these are obviously some of your fave shoes and you don't want to ruin them. I always do the shoe switch when driving to events with chance of rain. I learned my lesson when I ruined a pair of Burberry heals that I loved. If you are not taking a car, either carry a larger bag that the shoes will fit in if you can pull it off, or just don't wear the python. The nude patent will hold up in the rain.
Let us know how it goes. Good luck!