I've never used a cartomizer, but the 510-t is an atty with a spike inside it. The spike pokes into the tank, and the wick inside the spike draws the
e-liquid into the atomizer. Flavor is a bit muted compared to direct dripping, but it's reasonably close imho. Throat hit is a tiny bit lessened compared to direct dripping, but again, not too far off. In my experience the 510-t tastes pretty good, unless you happen to run it out of juice and keep
vaping until the atty is completely dry, in which case it'll taste like burnt atty. Not really an issue for me since the tanks are clear, just keep an eye on it and as soon as you notice vapor production and flavor start to decline the tank is probably empty and needs to be swapped out for a full one. The tanks hold a little less than 1ml, and come with little rubber caps which fit over the atty end of them so you can carry spares with you without having to worry about your juice leaking out.
Now the eGo-T on the other hand is a different animal (not that you asked about it, but still). It's the same thing in theory, but the tanks are larger which is kind of nice. On the other hand, they have wicking issues, leaking issues, the mouthpieces fall apart and become useless, and they provide much less flavor and throat hit compared to the 510-t. I have both, and I use the 510-t tanks and atties on my e-Go batteries and passthrough. YMMV.