I don't have the money to spend on a volcano.
Good. It's an unnecesary expense IMO.
how much more efficient would you say this vaporizer will be when compared to smoking herb.
MOST people find that ANY vape stretches their supply. Some will use half as much. Some even less. Some don't notice a big difference. It depends on different factors-like how much you were smoking and from what. As an extreme example, I know a guy who was burning through a lot of herb with bong use. He wanted to use less, so I loaned him a Purple-Days vape, which has a tiny bowl, but will deliver multiple, decent hits. He took to it right away and cut his consumption dramatically. With this vape, after a bowl or three, you're likely to say to yourself, 'I'm good for now', and just not load another for a while. Load a bowl on a full size whip vape like the DBV, and you'll normally have a lot more loaded than you can get in a PD/MZ bowl (.025-.05g). You're also likely to take considerably bigger hits than you can get from a PD. On the plus side, a couple of good sized DBV hits are likely to get you pretty blasted. OTOH, taking bigger hits than you can effectively process (huge vapor exhales), isn't efficient use of your supply. It's fun though. So, a vape like the PD is great for measured dosing, while a full sized whip vape like the DBV is harder to be efficient with. You certainly can load small amounts in a big bowl and take smaller, more manageable hits. It just isn't quite as enjoyable, used that way. It's like driving a sports car with fuel efficiency as your priority.
I have read about vaporizers producing a cleaner, more energetic high.
Because at low-medium temps you miss out on the toxic, couchlock inducing compounds you get at high temps and much more so with combustion. The strain you're using still makes a difference, but there's still a clear difference between the smoke and vapor high.
I mean if I'm smoking a heavy indica before bed, its still going to have that downer effect?
You mean vaping before bed? Personally, I've found that I can stay up late more easily by vaporizing, or vape a bowl of whatever strain, and get to sleep just fine. I don't recall hearing any complaints like 'vapor keeps me from getting to sleep'.