I made my first purchase based on the most common quoted reason of which you ask: I thought it would be impossible to switch unless the PV resembled a cigarette as much as possible. I don't really know if that's true or not, but just in case it is...
In any event, I ended up with a small cig lookalike which worked, but not too well... Having to recharge very often, having little flexibility of use, etc. And, on top of that, a cig lookalike is still too big and too heavy to really "trick the brain" into thinking you're holding a cigarette!
BUT! With the cig lookalike I did switch instantly, I had NO cigarette after my first
vape on my first kit. So they did
something right.
However, very-very soon thereafter, I realized that I reached their limit of usability - the annoyance of frequent switching for recharging, the impossibility of increasing power or playing around with shiny new attachments, well... it just stopped working in a matter of a week! I discovered that one feature of real cigarettes that the PV needs to emulate the closest is certainly not the form factor, but the
reliability. And that perfect consistency of the fact that every single time you want to smoke, you light it and you get
the same sensation without
any fiddle factor. That is what one needs.
No cigarette lookalike can replicate the reliability, and (I may get stoned for this) no unregulated PV can replicate the consistency. Period.
Therefore, I'd look for a durable, well built voltage regulated mod that takes high capacity
batteries that you can swap out (or, at the very least, battery-passthrough that can be vaped while charging). I would make sure I include the most reliable and fiddle free attachments - which probably are cartomizers, and get a couple of atomizers fo
juice testing purposes. Later you can branch out and test all the fancy clearo-fluxo-stardust-tornado-mizers out there.