No One. I've stayed in both and each is somewhat similar ..... no gambling.
Of the two you prefer, I'd suggest Vdara due to its location on the Strip and within CityCenter where there are many more options for dining and seeing 'stuff" without the need to walk long distances or hop in expensive taxis.
But don't be too surprised to discover that you're the only guest in the Vdara when you arrive.
Make sure to visit the Cosmo while there and try to find the secret pizza counter if you have nothing else to do.