A lot of factors should be taken into account; but the most important in my eyes, does it work with a minimum amount of resources needed. You should be able to tell once the site is generating enough traffic, but I agree with the others, have another programmer look it over. Programming, especially in web, should be up to today's standards; both front and back end. Debugging should be rather easy to turn off and on; a great trait to a well deserving programmer.
