I want to buy the HFS21 for the manual controls and zebra stripes features, however if I were to do that I'd have to borrow money, does the HFS20 offer all the same manual controls (Touch screen iris, apertures, white balance, etc) as the HFs21? Also what SDHC Cards are best for 24 mbps recording?

The HF S20 and S21 are completely identical in terms of controls, etc. So that's good news for you.

Search this forum for existing discussions about memory card recommendations.