The answer was the following: They were told that PD comes with all these extensions, which makes it really useful, but that these extensions are really buggy. Thats why they preferred using MAX.
Their fault I know, but it made me think ...
Wow, what a statement. MAX itself (not the addons) is buggy as hell. Last week i had real troubles to get MAX reliably working for a concert. If PD had the same graphical abilities as Max i would completely switch to PD. Yet, the graphical interface (or TCL/TK, respectively) is a real obstacle....
To my mind, the foremost problem is the incomplete or inscrutable documentation, that makes it difficult to get started with PD. Looking at the MAX (and jitter) package, one has to admit that Cycling have done really good work with their SDK documentation, help files and tutorials.
greetings, Thomas