Both cartomizers and atties are considered disposable, but how long they last seems to vary quite a bit between different users. The cartos are cheaper to replace--five prefilled cartos will cost me $12, and five atties will cost me $35--but as for which purchase will last the longest, I haven't the foggiest clue. Part of it is how they're treated, how they're cleaned, etc.
As for refilling, 510 carts are very easy to refill, but you may find yourself topping off constantly. Many people who use 510s either modify the cart or just
direct drip. I haven't tried many cart
mods because I'm just not that interested in fiddling with it, so when I use a 510 atty, I direct drip. That means I'm dripping
juice straight onto the atty every five to fifteen puffs; YMMV.
I don't have much experience with refilling cartos yet, but there are some really easy methods out there (LMK if you'd like links). Once a carto is filled, it can be used for much longer than a cart before needing refilling.
Having used both now, I can see why many people prefer one over the other. They are different vapes. However, since it *is* a personal preference, there's no definite "this one is better." TH is not an issue, in my opinion-- both products have made me choke when I drew for too long. If you want more vapor, and you don't mind topping off the cart or dripping, or you like the idea of playing with cart mods, then the 510 is your unit. If you want something that you can just pick up and use, go with the cartos.
I will say that I find the V4L premium cartos to be superior. I bought cartos from another vendor first, and had poor performance. I personally won't buy cartos from anyone else after that experience.
Whichever model you buy, you can buy adapters to use your
batteries with other atties/cartos, so you are not tied to one model, and you don't have to buy a whole new starter kit just to try a different model.