as said above, more options, and longer delay time. I went with the dd-6 over the dd-3 and am glad because the the warp function and the backwards delay are fun to play with. so is the looper...and it was only 30$ more so i thought meh might as well
Peavey JSX
Marshall 1960A
Ibanez S470 DXQM
Boss DD-6
Dunlop Original Crybaby
i was talking to a friend who owns the dd6 and he said he would rather have the dd3 because he said the dd6 fades out when you turn it off, and the dd3 is instant