I always use a scant and even that varies as to how much I move the needle. Some patterns have more pieces in a block than others and need more needle movement.
I have never used a full 1/4 in as my blocks will be too small. It is tricky and sometimes but rarely my blocks will be too big.
I dont really worry about the size of blocks except when My group needs a certain size block then it has to be perfect.
If it is just for a quilt Im making then blocks can be any size as long as they are consistant.