The problem with using drawing tools to produce your UML diagrams is that it makes it hard for someone else to maintain. How many times have you come across a document/wiki you need to update and just have a .PNG file for the sequence diagram, to make changes you now have to redraw the diagram from scratch! Rats!
Text to UML solves this problem by giving you the source code for a diagram. Now all you have to do is edit the source code and re-render and voila, your existing sequence diagram is up to date, lovely.
Other advantages are:
- It’s much quicker to make changes
- You don’t have to worry about consistent layout
- Diagrams can be generated
Martin Fowler also seems to prefer a text to UML approach