I'm sure most people who buy or rent the extended version are interested in seeing just that, so I suppose my situation is rather unusual. But this was a rental DVD and we didn't start viewing until fairly late, so we wanted to watch the shorter version. Apparently there has been little or no demand for the option of selecting either the original cinema version or the extended version from a menu.
There was an additional complication, due to the fact that I live in Germany. The rental DVD had German DD 5.1 as the default language. I set up my player (Toshiba SD-230E) to use the English DD 5.1 sound track with German subtitles, and then programmed the player to skip the new scenes (marked as such in the list of scenes).
Skipping the new scenes worked fine, but unfortunately the player "forgot" to continue in English with German subtitles! So I had to reset the sound track/subtitle settings after each jump. Rather distracting, believe me...