Others are addressing best use of land and cost to produce per ton/acre.  

You asked for best choice without regard to the above so here is my three choices:

1. Alfalfa Baleage   -- I believe it is better feed than alfalfa silage.  You get the whole plant ensiled with more of the plant juice intact within the stem.  Leaf loss is much less and the cattle get the benefit of the long stem hay versus the chopped feed.

2. Earlage  --  A great source of filler with energy.

3. Dry Shelled Corn (cracked)  --  Get 'em fat!