I have a 64 gig rom and 64 gig SD card. I am never going to fill both of them.... I have out about 20 gigs worth of movies in 720-1080p. 9 movies I believe. They are in the 64 gig SD card.
The 64 gig currently has 47.4 gigs free of 54.5 useable gigs. I've download adobe and updated the video app so far. That is it.
A 32 gig is perfectly good enough with an SD card, Unless you plan to download a lot of movies, music, and apps. I personally went for the 64 because there was the best buy deal on it(check the surface 2 forums), and I prefer having a lot of space available just in case I may need it.
OH!!! I also have a terabyte external hard drive to really hold huge files like my shows( Friends, how I met your mother-damn the last episode...-, and supernatural). So yeah. A 32 gig is perfectly fine if you have the SD card or external hardrive. The 3.0 usb port on the surface is very fast, so it can read and write on my hardrive fairly quickly. No need to move my shows, and waste space, to watch them.