Its the LPR on the DM9 (which the geo doesn't have) which makes it more able to shoot softer paint.
Look at the price comparison
DM9 £793.95 from LIPS
GEO £983.55 from Planet Eclipse
I am Currently Shooting the DM9, IMO the best gun i'v ever shot, it shoots where you point it and where you want it to go. I know of so many people from my own team and tigers 2 which have been so impressed by the accuracy of this compared to any other gun they have ever shot 'prevously'.
The gun does take a little more time to clean and relube, but its tested technology. IT WORKS.
Dye's service is as good as Planets. At the end of the day, you will be paying for
1)Styling
2)Price
3)reliability?(geos not been around as long)
IMO, get the DM9 and spend the rest of the money on paint to get pro like NEXUS who (OMG what a coincidence) shoot DM9's!