My personal favorite are 25yards/1, and 4pt/1TD. This makes the QB a valuable part of the offense, but still gives you reason to draft RB first, not throwing off the usual fantasy drafts too much.
My second favorite is 25yd/pt, 6pt/TD leagues. This actually makes the QB usually better than the RB, but because of value, RB is still drafted first. Also, if QBs get hurt, replacements can be sought on the WW.
The other two systems devalue the QB too much ... so I think in terms of realism, they shouldn't be used.
My $ 0.02.