I like the convenience of precuts, but don't like them because some of the pieces are wonky and smaller than they are supposed to be meaning I am having to adjust my seam allowance accordingly. I like yardage since if I can usually compensate for a wonky cut of for the fabric being off grain. That said, I mostly have yardage (and wayyyyy too much).
When I made my I spy quilts, I used 6.5" blocks and I bought 1/3 yard pieces since I wanted to have a strip to use in the piano key border and binding.