I use "my" 1/4 on blocks that will all be made by me and used for a single quilt. That way they will all be the same and no one else has to work with them (e.g., I might end up with all 12 1/4 inch blocks). But for a block swap, I use a scant 1/4 inch to make the block mathematically exact (like when it should be 12 1/2 inches) - that way makes it much better for another to use the blocks.
Why don't I use the scant all of the time? Because I have to make a manual adjustment to my machine every time I turn it on and it's easier to just use the foot guide and not adjust unless I have to!