I started
vaping using boge cartos and still use them almost 2 years later. The only difference between the regular length cartos and the xl cartos is that they are longer and hold a little more liquid. I have never noticed any difference in taste or performance given that they both work properly.
Advantages over clearomizers? For me, the boge cartos (sorry, I haven't tried any other brands) provide very good flavor and it is as good as the aspire bdc clearos I use. The advantage of the aspire clearos is that they hold more liquid and you don't have to keep adding liquid every time you use them.
pbusardo has some videos showing the inside of a carto, I think, so check out his site. He has videos on them too, as well as on clearomizers, which might explain them better if you want to know more. Hope this helped some.