I use 2.5 inches, but also like to leave that 1/4" of batting and backing beyond the quilt top. It gives the binding some substance, which I really prefer.
Have you tried the faux piping method? It uses 2 strips 1.5" of the piping and 1.25" of binding material. Sew them together, press seams open, then press in half. Sew on the back of the quilt, then turn to the front. It makes a wonderful piped accent. The best part is that you machine stitch in the ditch and no hand sewing.
Here is one tutorial. She gives reasons for pressing to one side or the other.
http://www.quiltscapesqs.com/2014/07...so-secret.html
I use this technique on any quilt with minkie backing, which I don't like hand sewing, and one others that I'm either happy to be done with, or can't imagine sitting for 3 weeks hand stitching at night. (Recently a 116"x116" king sized quilt for my parents.)