S.H.
keep in mind that as long as you get a he (high efficient) machine, it will only use the least amount of water needed to wash your clothes. I'd go for bigger (as long as it's "he" and you have space for it). I really don't know however much about the cubic feet though.... just get "he"... it is worth it.
*** I have not noticed difference in price with he detergents... I use much less of it... so I think it equals itself out.