For the Turning Twenty pattern I think the 20-piece fat quarter is really the best. It is probably more expensive than buying fabric by the yard, however, if you are putting lots of time into making a quilt you want it to be pleasing to you. So what is pleasing to you, more colors? It surely is a personal thing. Using your scrap box is a good way to use them and more economical, but not as much fun as going shopping for more. I have a quilt shop that has 20-piece bundles already put together so I can look and feel them before I decide to buy. Good luck with your decision.