I am not a quilt "judge" but have entered a lot of quilt shows and down quite well. It has been my experience that it has been better for me to hand sew the binding to the back, because I can get it more perfect than sewing it down on the front by machine. I do tack the binding both ways but have never been able to master machine sewing the binding down to look as "perfect" as hand sewing it down --- so for my show quilts I always hand tack it to the back.
I make a lot of quilts in year's time and don't hesitate to sew the binding to the front of the quilt by machine if I am not going to show it. And I can get it to look pretty good, but it is never as perfect as I can get it sewing it by hand. Binding is one the of things that the judges do look at closely. If the technique you use for your binding is not perfect, then they are not going to go look any further especially in the big shows where the competition is very stiff. In a smaller or local show you could probably get by with sewing it on the front by machine. ------- Just my opinion for whatever it is worth. Hope it helps.