Depends what you're going to use it for. FLAC audio files take up a lot of space. If you eventually want to take advantage of USB audio, or even the default Wolfson audio, then good quality audio source takes up a lot of space. So do 720p movies. You've got that 720p screen. Don't you want to use it for watching movies that utilize it to its utmost? 2-4GB for a movie.
Depends if you are going to root etc. There is a camera mod available on custom roms that enables you to shoot video at roughly twice the bit rate of the stock camera and hence at a much higher quality. Using something like that would likely demand the higher transfer rate.
I would go for a class 10 64GB
- size and
performance. Is it necessary for you to compromise?
Reserve the 32GB internal memory for apps that take up hundreds of megabytes? I know I've been reveling in my /data space for installing apps after coming from my HTC Desire.