Pretty tough decision, because its comparing 2 different arguments (both with great points). Passion for the current V8/S65 engine will continue, but if you are already thinking you may get the next M3/4 (despite no one truly knowing exactly what it will end up being like, albeit probably just as amazing), there probably wouldn't be a point to pay for a customized M3, other than getting the wonderful experience of ED.
Do you have any experience driving the current M3? If you love everything about it, I'd say customize one to your liking and opt for the ED. But if you have some hesitations and are truly concerned about it being outdated in 2 years, you probably should just get a 2011 and enjoy it while we wait to see what BMW has in store for us next go around.
If it were me, I'd do the ED and keep it for 3 years, then think about it again at that point. (But I think the high-revving V8 will be hard to get rid of