DM6...
Heavier? yes by around 75g's (negligable?)
But my findings are: (having owned 06 ego and DM6)
-More accurate, theoretically a spool valve will always be more accurate than rammer/bolt design.
-No open, moving parts, meaning much harder to get water/****e inside the gun (and you know how bad the weather can be over here)
-Much quieter, is this better?, i dunno it sounds cool tho.
-Much smoother
-Much less kick
But
-Ego seems better for parts/tech assistance (nicky t is an absolute legend!)
-Easier to maintain (but the DM is by no means hard)
-IMO the ego is easier to get to shoot fast due to the new filters
-Everyone has one so if summat breaks/goes missing at a tourney you will more than likely find someone with a spare or who knows how to fix it.
Its the price that would make my mind up, you can get as new (ie a tourney or two) DM6's for £500ish, or a new Ironman for £750 from heaven whereas the SL66 i doubt you'll get for less that £800
used or £1100 new.
Failing that get a used 06 like the one i just sold in minty fresh condition with ups for £550!...much better value, and you wont notice any difference other than looks with a '66