To echo what Gaz said,
I have also owned both, I found the GEO 2 easier to work with than the DM12 with regard to settings specifically the trigger.
There is less "options" on the DM12 if you are the kind of person that likes to fiddle & tweak your setup
Mainly comes down to personal choice, I found the DM12 less comfortable in my hands but that is totally a personal choice, I prefer a smooth anodised finish to a grippy rubber one
That said I sold them both & now shoot an Empire Axe not for sponsorship reasons, because I can have 2 for the price if one