What is the advantages and disadvantages of error handling and dialog controls?

Answer 1

The advantage of error handling is that your program doesn't explode when it sees something that it shouldn't. Error handling allows you to tell your program how it should react in those situations. The program may still have to close, but you can make it do so more gracefully (clean up data, close database connections/file pointers, etc.)

The only real disadvantage is it makes your code a bit larger, but it is a critical trade off, especially for more mission critical applications.