I would say for The Ego , that the EGo Mega is better and the colossal is better for other uses. The Ego Mega fits great on the Ego batts and looks like it belongs on there, holds ALLOT of liquid, and has perfect air flow....You would need an adapter to use this with most other
devices.
The Colossal works with any 510 and dosent hold quite as much liquid, but it does come in 801 and 510 connection in stainless steel and also comes in Clear in the 510 version. All of the Colossals are also available in an assortment of resistances.
Hope this helps some. Thanks
Drew