I always kind of looked askance at cartomizers and the polyfill and such but they ultimately transformed my vaping into a more sustainable / hassle-free process once a friend of mine gave me a freebie to check out. Years later, tl;dr version of below, I have a bunch of new Boge poly cartomizers, dual coil mega cartomizers, etc, all in the packaging purchased years ago, and I got back into vaping because of the gloriousness of modern tank technology. And I'm behind the curve, having only tried:
Kanger ProTank II Mini, Kanger TS3, Kanger EVOD (no luck with the last one, working on airflow issues but the others are too good to make it worth my while during the honeymoon period).
I also use some CE4 clearos for my non-top-shelf juices but the authentic ProTank II Mini and TS3s will keep me away from poly cartomizers as long as they exist.
On to the poly cartomizer saga...
I never had any trouble getting at least 20 drops / ~1ml into one and I usually either ran 2.0ohm cartos at 3.7-4.0V or 3.0-3.2 at 5V.
For the guy who mentioned bronchitis, I ultimately settled into using my ProVari to enjoy 2.0 and 3.0ohm cartomizers most of the time for a solid year. I noticed that it did tend to drag my colds on longer than usual, being a recent father who would get sick from everything my toddler got, it seemed to prolong the post-cold lung crud and ultimately bronchitis that I usually developed. But it was clean enough compared to smoking for me to be somewhat compelled to use it as much as I could get away with every day, giving me a nice cumulative irritation.
Before I quit smoking, I first noticed that I went from getting a noticeable cold every couple years to getting really crappy colds throughout the year, in part due to the kid and in part probably just due to being older and not taking great care of myself. I can't fairly blame the increased frequency of colds on my kid and age without also blaming the duration and incidence of bronchitis, but suffice it to say I was drawn to the ProVari + Boge cartomizer but it definitely seemed to be rough the next day and increasingly would be rough for the first drag of the day, and I'd be like "OK I drank enough water and am hydrated let's try this...GACK." I had plenty of variety to choose from and it wasn't anything like a bad box or bad batch; just a progressive increase in discomfort and irritation with plenty-good taste.
To make a long story short I got progressively more and more irritated by cartomizers and gravitated more to full-VG juices that didn't work great in cartomizers. I'd cut them with other juices to make it work but they still irritated me plenty. So it's plenty possible that I have a PG sensitivity / allergy and direct dripping didn't make it apparent because it was fiddly and time consuming and not as mindlessly easy to take in tons of hits as with cartomizers. This is what fair-mindedness should look like, but I sure want to blame the Boges!
I found myself dripping Alien Visions juice on low resistance atomizers on an old box mods instead of my ProVari, because it seemed to gripe (with AW IMR batts) no matter what voltage I used.
I didn't like direct dripping all of the time; I do it but I want more convenience at work and such.
Back then the entry level clearomizers were just starting to get modded into "MAP tanks" and whatnot and a friend of mine was really into carto-tanks but I wasn't super impressed. I tried various mega / dual-coil cartomizers and didn't like 'em. I tried early first-generation clearomizers and liked them at first and then they fell apart constantly and were wildly inconsistent and just seemed like a bad idea not ready for prime time.
At the end of the day I had a ton of Boge cartos and that was my system, and I just hit a wall where it made me too irritated and wheezy and miserable to continue that system, especially during or after colds, so the ProVari started spending more time in my vape drawer. I keep most inhalation to a minimum when sick so I'd use snus or other means to keep getting nicotine and found myself more and more sensitive to the point where I could barely stand a few drags ever, unless I'd just taken a shower or was drunk and willing to feel it the next day.
Long story short, I stuck with snus almost exclusively for 18 months or so and then bought a crappy VUSE kit just to see how "cig-a-likes" had come along. First of all, too big and clunky to really even be a "cig-a-like" but I liked it for awhile and was being strangely ambivalent about the stockpile of stuff I already had, preferring to slum it with the VUSE until its cartomizers also started to make me increasingly sensitive and irritated when vaping. It took about 2 months for that to happen and then I finally started exploring my old stuff and picking up some new Ego twist batteries due to losing my ProVari in a move (!!!).
But here's the "let's be honest" part: I'm a lifelong MMJ user and I mostly smoke; when I vaporize it it tends to irritate me more than smoking, but I'm trying to phase that out. So you have that confounding factor in my whole story, and as your friendly local doctor will tell you, everyone has these elaborate difficult experiences in life but won't always fill you in on the details it takes to provide a comprehensive answer.
Long story short, MMJ can co-exist with me using those Kanger tanks and all-VG juice, and does not co-exist with poly cartomizers or higher PG juices, though I haven't done enough double-blind experiments to say the latter with full confidence, teasing apart juice vs. PG vs. VG vs. atomizing apparatus
Extra tidbit of information; I bought a $35 current gen Blu starter kit because I bought one early on and always had some sentimental appreciation for it despite it sucking. Even back then with the crappy cartridges I liked using them in a few settings like going out for dinner with family and I lost both batteries in a running-through-a-park-like-a-child-for-no-reason incident so they left me in honor, in legendary "I miss them" status before they could die 2 weeks after buying them. (Note: the new batts are more than two weeks old and doing fine, I'm just saying the first Blu set didn't get a chance to disappoint me and die without honor, especially because a the time they had some crazy cartridge deal so I just kept opening new ones after the 10 drags of decent vapor before "all gone" without fiddling too much and even back then it was supplemental to other gear).
Circle back to now, I know quite a bit about vaping, but not enough about the importance of not losing a ProVari I painstakingly hunted and sniped for in the classifieds years ago...and I bought yet another Blu starter kit! ... is wrong with me? I don't know but it's not terrible, and I found myself doing the same thing tonight, using it when going out with the family, first doing some sledding in the snow at a hill nearby, with the PCC nestled away safely in my coat. Why bring up the Blu? I dunno, but I like their cartomizers and would like to learn more about them. They don't hold up to repeated chain drags like tanks, at all, but they seem a lot better and smoother than the Boges I still have.
In my experience if you're used to Boge cartomizers you'll be blown away by the chain dragging capability of a good tank even if you don't really like chain dragging. I don't do it for very long but I like the "buffering" or heat absorption that kicks in really fast (at least at 2.4 ohm) so that you never had a burned crappy hit because you broke your normal "cadence" and took 3 puffs too fast.
