That depends on who you ask. You ask an Eclipse fan and they will say the Ego, ask a Dye fan and they'll say the DM, with that level of marker it's all personal preference really.
Both of them will shoot consistently at whatever rate you want, both will get through enough pods for a game on a single tank of air, both will work well for a long time as long as you perform basic maintenance on it and don't neglect it.
Essentially they are both great markers and will do what you need them to day in, day out without fail.
If you're thinking of buying one of them then what you should do is find members near you, or a shop near you, who will let you get your hands on those markers, because your decision should come down to which marker you like the feel of best.