Is 1cc of Juvederm Voluma more volumizing than 1 cc of Juvederm Ultra / Ultra Plus? How much volume does 1cc ultimately provide?

your observations are correct with Artefill and Radiesse. Unfortunately, none of the HA fillers are nearly as hydrophillic or inflammatory as the above. Voluma will not swell nearly as much due to the Vycross technology and also why it lasts so much longer. Juvederm Ultra Plus does not have quite the G prime (thickness) that Voluma has, but will swell much more. The swelling does not last, however. In general, the swelling will all be gone by 2 weeks. 

Voluma and Juvederm will correct only a cc of volume each. There is no extra volume because of the hydrophillic effect. My findings are that Bellafill is not as strong a volumizer as you describe. Radiesse is a 1.5 cc syringe and probably does more than that as far as volume. The most robust filler is Sculptra. It has been said that a vial of Sculptra is probably about 4 cc of HA filler. Large volumes of HA filler, like the 10cc you want, tend to look abnormal when placed in a patient. Things look edematous, puffy.