I was also in the same situation, deciding between HerbalAire and volcano. I really couldn't find any good reviews on the HA that didn't seem slightly biased, so I ate the additional cost and bought a volcano. I love it. I regret the price, but the amount I smoke will make up for it.

And about the HA extracting more from the herb, I'm not hugely worried about it. I don't vape all the way every time. Once the taste starts getting bad, I put it to the side. I'm going to use the duff (vape remains) to cook with or something, so in the end, I still win.