You are looking at two mods on complete opposite sides of the spectrum. Yes, they are both tube mods but the build quality along with internal make up is completely different. It's like test driving a Honda Civic and a Audi A8. If you can afford the A8, why in the world would you even be thinking about the Civic? If you held both devices in your hand, it would become instantly apparent as to why the Provari costs more money. Now, if you really want the L-Tube, at least wait until version 1.5 is released. It is able to drive dual coil cartos correctly.
Here is a good informative review of the Lava Tube. After watching it, you will understand what I mean by driving dual coil cartos correctly.