Okay Stupid!
I have a big difference: the vivis plastic completely screws off the metal. The clearos don't, and are fused to metal. With the different rates of expansion / contraction on the clearos, mine started leaking where the metal and plastic are fused. It now sports a black stripe of electrical tape, which doesn't look too bad on the black eGo with the smoked glass clearo. Isn't that cute? My first "mod".
I like the hit better from the clearo, but the vivi is great also and I do use them both daily, along with my glass tanks. I mix up the flavors a lot.