I think it is a preference. However our guild is donating to Quilts of Valor for our service folks, and there are several hard and fast rules. Separate binding is one of them. And I am not that experienced, but I have been paying attention, and all the quilts that win ribbons in the shows I have been to have separate binding.
So if it is for family, friends, charity, self or utility, I see no problem. But I would certainly take the extra time and effort if it was for a show or a special project like QoV.