What I typically do is get the 1-disc (for most movies I will never touch the extras) or hold out for a loss-leader sale where I can get the Special Edition for around the same price as the regular (that's how I picked up Lord of War, for example).
Only for favorite or "event" movies like LOTR, SW, Kingdom of Heaven, etc. do I bother with the loaded editions at full price. For KOTCS I'll hold out for a holiday sale until I can get the 1-disc for $10 or so.