Every situation is different. The degree of restoration, the value, and the likes and dislikes of the owner are all a concern when considering restoration. Lets say you own a rare hanging chandelier but the original hanging device is broken and you are not able to use it in your home. A professional restoration would allow you to enjoy the use of the fixture. The value of the fixture if restored properly would not be as high as if it were all original.
Don't make rash decisions when considering restoration. Consult a professional appraiser or dealer. Weigh the options and then make an intelligent choice. Over the years we have seen too many costly mistakes that people have made concerning restoration.