Actually I own Both!!
They are great, I prefer the Vapezilla because it has the digital read out. I also have a little motor I guess you would call it that plugs into the side of it that will force air through the unit. It is almost too much! The volcano is great too and I have been using that one as of late, (broke the glass whip for the other one). As far as what you use in them, quality of flower will always give you better results, that being said I would go out on a limb and suggest that no matter the quality you will get the most out of your med with a vaporizer. To be honest I have never vaped anything but high grade. Gotta love Cali!