A 1/4" seams allowance should be fine for most projects. The only time a scant would really matter is if you have small piece and have a "gazillion" of them in your project. More important is to use the same sewing machine for the entire project. I haven't figured it out (and probably never will), but 1/4" seam on one machine isn't necessarily 1/4" seam on another, even if you use a 1/4" seam foot. Crazy, but true.