Granted these are probably the ones you already thought of.
Advantages:
1) It's easier to use a GUI to create a web page
2) You can focus on the layout without having to worry about minor details
3) You don't have to understand much about HTML/CSS
Disadvantages:
1) It often generates unnecessary code creating a bloated page
2) The minor details can cause a page to not be W3C compliant
3) You get a benefit of making code cleaner and more compliant across different browsers