I haven't used a Vapir One, but have heard many reports on it over the years, as well as other Vapir products.

All their models have digital displays and a short, 90 day warranty. That's a bad combination, and the company has developed a rep for the poorest reliability of any brand name. And with the model One, you also have a fan to worry about as well as the display. Although it's small, it's not considered a portable either, since you have to use AC.

If the DBV is too large/cumbersome to suit you, and you want to stay under $200 (and if AC use is acceptable), I'd consider the Purple-Days. It has high efficiency, great build quality, small size (like a beer can), and doubles as an essential oil diffuser. It's been reported to pass the 'cop confiscation' test too. It has a 3 yr. warranty with very little to go wrong on it. It gets most of the use in my house, although I also use an SSV sometimes for bigger hits.

Other, even more portable options, are the Magic Flight Launch Box (about $90, very small, powered by AA size rechargable battery, unconditional lifetime warranty), and the iolite (no flame butane-catalytic, $200+, about cell phone size, 2 yr. warranty). I have both of these and they're both nice stealth portables.

You should be able to find videos of all these models in action on youtube. Quite a few on the Purple-Days, both in use and interesting build and durabiltiy vids by the builder.