Both of those ecigs are kits that are built around the eGo battery. I'm not familiar with the eGo C system, but it appears to be a tapered tank and or a sleeved cartomizer setup. The eGo Vision set offered there uses the Vision Clearomizers. Clearomizers last for quite a while if they are cleaned on a semi regular basis with vodka or rubbing alcohol. If you decide not to clean them, expect a week or two of usage and then the atomizer head will need to be replaced. It takes only a few seconds and the heads are 1-2 pounds. (sorry, only $ signs on this keyboard.) $1.00-3.00 here in the U.S., depending on where you go to buy them.
You may want to consider buying an eGo Twist, rather than a standard eGo. The standard eGo produces a constant 3.4 volts, the Twist is adjustable from 3.2 to 4.8 volts.
Whatever choice you make, you will get longer life and more vapour from the eGo devices than you have been getting from your DSE901.