Hi Francesca, and welcome to the forum.
I don't know which product you are using, but if you go to the suppliers list in the forum and check out their websites, you can compare. I personally have only penstyles, which I got because the cartridge and
batteries were supposed to last longer between refilling and charges compared to the other models. Maybe they do, but the life of the
batteries decays so fast that I am going to have to spend way more for e-cigs than I did when I only smoked regular ones (now I limit myself to 3-4 a day, from about 22 before).
From your name you definitely sound Italian.... I am from Italy, too (Milan, in fact), although I live in NC (after having lived for 8 years in Denmark). If you are, ciao, e benvenuta....