With a manual you will be $8000 better off (in your pocket) and I am sure when it come to trading in one day you will not regret it. When I sold my E46 M3, I managed to get the price I wanted because it was a manual. There was a massive shortage of manual cars in the E46 second hand market.
The novelty is there but then at the end of the day you should know what will make you happier. M-DCT is fantastic and a brilliant track tool, but when it comes to driver involvement and enjoyment I don't think anything out there can beat the manual box in a BMW /// car. This is my opinion.
One thing I noticed is people who are new to M cars went with SMG and now M-DCT. But those who have driven previous generation /// cars have always stuck by the manual except for a handful.
If you want to impress your mates and be a lazy driver then M-DCT is for you. If you want to enjoy what an M car is then a manual will give you
Sheer Driving Pleasure 