My 1/4 seam foot for my machine keeps the needle position just a hair shy of the 1/4 inch mark, so as long as I use the guide on the foot all my seams are the same.
Regardless of whether it's a 1/4 inch or a scant 1/4 inch, what is important is ALL the seams must be the same width.....if your seam allowances vary, even the tiniest bit in the project, you have a headache in the making. :D