It comes down to personal choice in the end. The DM6 is the latest gun out, but there are people having issues with them, just look on pbNation. They are still working out the wrinkles in my opinion.
That said, get the best gun for your money. I have had a DM5 and now run a DMC, with no problems. When a problem occurs, it is usually an oring issue, no biggy. My gun is very consistent and rips.
If I had to give a downside, it would be that they do not like the cold weather but if you know what you are doing and adjust to suit the weather, its then not an issue.
There are some good prices on DMC's at the minute if you look around with people wanting to jump on the newest marker out bandwagon, take advantage of this fact.
Hope you get what you want.