I use a very large poly board
24 x 18
I like a lot of cutting spaces so it's important to me.
When I buy new ones I look at how I set up my prep area, I usually have 3 to 4 bowls along the top of the board to put items into as I'm prepping, and one trash bowl or bag (sometimes I just roll down a plastic bag as you can mold it into your work space)
I do buy my boards fromhttp://www.catskillcraftsmen.com/
not as high end as the other two mentioned but very solid boards and reasonably priced. They also have a lot of board maintenance videos to help you take care of an end grain board