Now that I'm using one, I think I can finally answer one of these questions
The carto offers less fussing with bottle squeezing or squonking as we call it. I run mostly LR306s on my mods and I do a fair amount of squonking....about once every 5 or 6 draws. With the Carto...I'm getting more like 10-15 draws before I re-juice it. To me, its not that big of a deal, but for some it makes a world of difference.
The hits also seem really consistant with lots of vapor.
Now, the drawbacks....I get better, crisper flavors from my atties. But the flavor of the cartos isn't bad...just more mellow. Which is a good thing with some juices. And after 2 days of use, my carto's draw has tightened up considerably and I think I may be lucky if I can finish the day without changing it. I can get months out of most of my atties.
My opinion? I think the cartos are a great way for a person who is new to mods to become acquainted with their device with relatively little hassle. The learning curve on 510 atties isn't that big of a deal, but the 306s can be a challenge to learn.
it also retains the juice better, so there is less that ends up in the reservoir unless you're really over juicing it. My reservoir on my mod with the carto is completely dry.